diff --git a/SabreTools.Metadata.DatFiles.Test/ItemDatabaseTests.cs b/SabreTools.Metadata.DatFiles.Test/ItemDatabaseTests.cs
index 887c5d94..d25085fd 100644
--- a/SabreTools.Metadata.DatFiles.Test/ItemDatabaseTests.cs
+++ b/SabreTools.Metadata.DatFiles.Test/ItemDatabaseTests.cs
@@ -23,9 +23,13 @@ namespace SabreTools.Metadata.DatFiles.Test
             };
 
             var dict = new ItemDatabase();
+
             long sourceIndex = dict.AddSource(source);
+            disk.SourceIndex = sourceIndex;
             long machineIndex = dict.AddMachine(machine);
-            _ = dict.AddItem(disk, machineIndex, sourceIndex, statsOnly: false);
+            disk.MachineIndex = machineIndex;
+
+            _ = dict.AddItem(disk, statsOnly: false);
 
             DatItem actual = Assert.Single(dict.GetItemsForBucket("default")).Value;
             Disk? actualDisk = actual as Disk;
@@ -42,9 +46,13 @@ namespace SabreTools.Metadata.DatFiles.Test
             DatItem disk = new Disk { Name = "item" };
 
             var dict = new ItemDatabase();
+
             long sourceIndex = dict.AddSource(source);
+            disk.SourceIndex = sourceIndex;
             long machineIndex = dict.AddMachine(machine);
-            _ = dict.AddItem(disk, machineIndex, sourceIndex, statsOnly: false);
+            disk.MachineIndex = machineIndex;
+
+            _ = dict.AddItem(disk, statsOnly: false);
 
             DatItem actual = Assert.Single(dict.GetItemsForBucket("default")).Value;
             Disk? actualDisk = actual as Disk;
@@ -61,9 +69,13 @@ namespace SabreTools.Metadata.DatFiles.Test
             var file = new File { SHA1 = "deadbeef" };
 
             var dict = new ItemDatabase();
+
             long sourceIndex = dict.AddSource(source);
+            file.SourceIndex = sourceIndex;
             long machineIndex = dict.AddMachine(machine);
-            _ = dict.AddItem(file, machineIndex, sourceIndex, statsOnly: false);
+            file.MachineIndex = machineIndex;
+
+            _ = dict.AddItem(file, statsOnly: false);
 
             DatItem actual = Assert.Single(dict.GetItemsForBucket("default")).Value;
             Assert.True(actual is File);
@@ -79,9 +91,13 @@ namespace SabreTools.Metadata.DatFiles.Test
             DatItem file = new File();
 
             var dict = new ItemDatabase();
+
             long sourceIndex = dict.AddSource(source);
+            file.SourceIndex = sourceIndex;
             long machineIndex = dict.AddMachine(machine);
-            _ = dict.AddItem(file, machineIndex, sourceIndex, statsOnly: false);
+            file.MachineIndex = machineIndex;
+
+            _ = dict.AddItem(file, statsOnly: false);
 
             DatItem actual = Assert.Single(dict.GetItemsForBucket("default")).Value;
             Assert.True(actual is File);
@@ -101,9 +117,13 @@ namespace SabreTools.Metadata.DatFiles.Test
             };
 
             var dict = new ItemDatabase();
+
             long sourceIndex = dict.AddSource(source);
+            media.SourceIndex = sourceIndex;
             long machineIndex = dict.AddMachine(machine);
-            _ = dict.AddItem(media, machineIndex, sourceIndex, statsOnly: false);
+            media.MachineIndex = machineIndex;
+
+            _ = dict.AddItem(media, statsOnly: false);
 
             DatItem actual = Assert.Single(dict.GetItemsForBucket("default")).Value;
             Assert.True(actual is Media);
@@ -122,9 +142,13 @@ namespace SabreTools.Metadata.DatFiles.Test
             };
 
             var dict = new ItemDatabase();
+
             long sourceIndex = dict.AddSource(source);
+            media.SourceIndex = sourceIndex;
             long machineIndex = dict.AddMachine(machine);
-            _ = dict.AddItem(media, machineIndex, sourceIndex, statsOnly: false);
+            media.MachineIndex = machineIndex;
+
+            _ = dict.AddItem(media, statsOnly: false);
 
             DatItem actual = Assert.Single(dict.GetItemsForBucket("default")).Value;
             Assert.True(actual is Media);
@@ -145,9 +169,13 @@ namespace SabreTools.Metadata.DatFiles.Test
             };
 
             var dict = new ItemDatabase();
+
             long sourceIndex = dict.AddSource(source);
+            rom.SourceIndex = sourceIndex;
             long machineIndex = dict.AddMachine(machine);
-            _ = dict.AddItem(rom, machineIndex, sourceIndex, statsOnly: false);
+            rom.MachineIndex = machineIndex;
+
+            _ = dict.AddItem(rom, statsOnly: false);
 
             DatItem actual = Assert.Single(dict.GetItemsForBucket("default")).Value;
             Rom? actualRom = actual as Rom;
@@ -170,9 +198,13 @@ namespace SabreTools.Metadata.DatFiles.Test
             };
 
             var dict = new ItemDatabase();
+
             long sourceIndex = dict.AddSource(source);
+            rom.SourceIndex = sourceIndex;
             long machineIndex = dict.AddMachine(machine);
-            _ = dict.AddItem(rom, machineIndex, sourceIndex, statsOnly: false);
+            rom.MachineIndex = machineIndex;
+
+            _ = dict.AddItem(rom, statsOnly: false);
 
             DatItem actual = Assert.Single(dict.GetItemsForBucket("default")).Value;
             Rom? actualRom = actual as Rom;
@@ -195,9 +227,13 @@ namespace SabreTools.Metadata.DatFiles.Test
             };
 
             var dict = new ItemDatabase();
+
             long sourceIndex = dict.AddSource(source);
+            rom.SourceIndex = sourceIndex;
             long machineIndex = dict.AddMachine(machine);
-            _ = dict.AddItem(rom, machineIndex, sourceIndex, statsOnly: false);
+            rom.MachineIndex = machineIndex;
+
+            _ = dict.AddItem(rom, statsOnly: false);
 
             DatItem actual = Assert.Single(dict.GetItemsForBucket("default")).Value;
             Rom? actualRom = actual as Rom;
@@ -216,9 +252,13 @@ namespace SabreTools.Metadata.DatFiles.Test
             DatItem rom = new Rom { Name = "item" };
 
             var dict = new ItemDatabase();
+
             long sourceIndex = dict.AddSource(source);
+            rom.SourceIndex = sourceIndex;
             long machineIndex = dict.AddMachine(machine);
-            _ = dict.AddItem(rom, machineIndex, sourceIndex, statsOnly: false);
+            rom.MachineIndex = machineIndex;
+
+            _ = dict.AddItem(rom, statsOnly: false);
 
             DatItem actual = Assert.Single(dict.GetItemsForBucket("default")).Value;
             Rom? actualRom = actual as Rom;
@@ -237,9 +277,13 @@ namespace SabreTools.Metadata.DatFiles.Test
             DatItem item = new Rom { Name = "item" };
 
             var dict = new ItemDatabase();
+
             long sourceIndex = dict.AddSource(source);
+            item.SourceIndex = sourceIndex;
             long machineIndex = dict.AddMachine(machine);
-            _ = dict.AddItem(item, machineIndex, sourceIndex, statsOnly: true);
+            item.MachineIndex = machineIndex;
+
+            _ = dict.AddItem(item, statsOnly: true);
 
             Assert.Empty(dict.GetItemsForBucket("default"));
         }
@@ -253,9 +297,13 @@ namespace SabreTools.Metadata.DatFiles.Test
             DatItem item = new Rom { Name = "item" };
 
             var dict = new ItemDatabase();
+
             long sourceIndex = dict.AddSource(source);
+            item.SourceIndex = sourceIndex;
             long machineIndex = dict.AddMachine(machine);
-            _ = dict.AddItem(item, machineIndex, sourceIndex, statsOnly: false);
+            item.MachineIndex = machineIndex;
+
+            _ = dict.AddItem(item, statsOnly: false);
 
             Assert.Single(dict.GetItemsForBucket("default"));
         }
@@ -322,9 +370,15 @@ namespace SabreTools.Metadata.DatFiles.Test
             // Setup the dictionary
             var dict = new ItemDatabase();
             long sourceIndex = dict.AddSource(source);
+            rom1.SourceIndex = sourceIndex;
+            rom2.SourceIndex = sourceIndex;
+
             long machineIndex = dict.AddMachine(machine);
-            dict.AddItem(rom1, machineIndex, sourceIndex, statsOnly: false);
-            dict.AddItem(rom2, machineIndex, sourceIndex, statsOnly: false);
+            rom1.MachineIndex = machineIndex;
+            rom2.MachineIndex = machineIndex;
+
+            dict.AddItem(rom1, statsOnly: false);
+            dict.AddItem(rom2, statsOnly: false);
 
             dict.ClearMarked();
             string key = Assert.Single(dict.SortedKeys);
@@ -347,9 +401,13 @@ namespace SabreTools.Metadata.DatFiles.Test
             DatItem item = new Rom();
 
             var dict = new ItemDatabase();
+
             long sourceIndex = dict.AddSource(source);
+            item.SourceIndex = sourceIndex;
             long machineIndex = dict.AddMachine(machine);
-            _ = dict.AddItem(item, machineIndex, sourceIndex, statsOnly: false);
+            item.MachineIndex = machineIndex;
+
+            _ = dict.AddItem(item, statsOnly: false);
 
             var actual = dict.GetItemsForBucket(null, filter: false);
 
@@ -366,9 +424,13 @@ namespace SabreTools.Metadata.DatFiles.Test
             DatItem item = new Rom();
 
             var dict = new ItemDatabase();
+
             long sourceIndex = dict.AddSource(source);
+            item.SourceIndex = sourceIndex;
             long machineIndex = dict.AddMachine(machine);
-            _ = dict.AddItem(item, machineIndex, sourceIndex, statsOnly: false);
+            item.MachineIndex = machineIndex;
+
+            _ = dict.AddItem(item, statsOnly: false);
 
             var actual = dict.GetItemsForBucket("INVALID", filter: false);
 
@@ -385,9 +447,13 @@ namespace SabreTools.Metadata.DatFiles.Test
             DatItem item = new Rom { RemoveFlag = true };
 
             var dict = new ItemDatabase();
+
             long sourceIndex = dict.AddSource(source);
+            item.SourceIndex = sourceIndex;
             long machineIndex = dict.AddMachine(machine);
-            _ = dict.AddItem(item, machineIndex, sourceIndex, statsOnly: false);
+            item.MachineIndex = machineIndex;
+
+            _ = dict.AddItem(item, statsOnly: false);
 
             var actual = dict.GetItemsForBucket("machine", filter: true);
 
@@ -404,9 +470,13 @@ namespace SabreTools.Metadata.DatFiles.Test
             DatItem item = new Rom { RemoveFlag = true };
 
             var dict = new ItemDatabase();
+
             long sourceIndex = dict.AddSource(source);
+            item.SourceIndex = sourceIndex;
             long machineIndex = dict.AddMachine(machine);
-            _ = dict.AddItem(item, machineIndex, sourceIndex, statsOnly: false);
+            item.MachineIndex = machineIndex;
+
+            _ = dict.AddItem(item, statsOnly: false);
 
             var actual = dict.GetItemsForBucket("machine", filter: false);
 
@@ -423,9 +493,13 @@ namespace SabreTools.Metadata.DatFiles.Test
             DatItem item = new Rom();
 
             var dict = new ItemDatabase();
+
             long sourceIndex = dict.AddSource(source);
+            item.SourceIndex = sourceIndex;
             long machineIndex = dict.AddMachine(machine);
-            _ = dict.AddItem(item, machineIndex, sourceIndex, statsOnly: false);
+            item.MachineIndex = machineIndex;
+
+            _ = dict.AddItem(item, statsOnly: false);
 
             var actual = dict.GetItemsForBucket("machine", filter: false);
 
@@ -460,9 +534,13 @@ namespace SabreTools.Metadata.DatFiles.Test
             DatItem item = new Rom();
 
             var dict = new ItemDatabase();
-            long machineIndex = dict.AddMachine(machine);
+
             long sourceIndex = dict.AddSource(source);
-            long itemIndex = dict.AddItem(item, machineIndex, sourceIndex, statsOnly: false);
+            item.SourceIndex = sourceIndex;
+            long machineIndex = dict.AddMachine(machine);
+            item.MachineIndex = machineIndex;
+
+            long itemIndex = dict.AddItem(item, statsOnly: false);
 
             var actual = dict.GetMachineForItem(itemIndex);
             Assert.Equal(0, actual.Key);
@@ -497,9 +575,13 @@ namespace SabreTools.Metadata.DatFiles.Test
             DatItem item = new Rom();
 
             var dict = new ItemDatabase();
-            long machineIndex = dict.AddMachine(machine);
+
             long sourceIndex = dict.AddSource(source);
-            long itemIndex = dict.AddItem(item, machineIndex, sourceIndex, statsOnly: false);
+            item.SourceIndex = sourceIndex;
+            long machineIndex = dict.AddMachine(machine);
+            item.MachineIndex = machineIndex;
+
+            long itemIndex = dict.AddItem(item, statsOnly: false);
 
             var actual = dict.GetSourceForItem(itemIndex);
             Assert.Equal(0, actual.Key);
@@ -517,7 +599,7 @@ namespace SabreTools.Metadata.DatFiles.Test
 
             Machine machine = new Machine { Name = "game-1" };
 
-            DatItem datItem = new Rom
+            DatItem item = new Rom
             {
                 Name = "rom-1",
                 Size = 1024,
@@ -526,9 +608,13 @@ namespace SabreTools.Metadata.DatFiles.Test
             };
 
             var dict = new ItemDatabase();
+
             long sourceIndex = dict.AddSource(source);
+            item.SourceIndex = sourceIndex;
             long machineIndex = dict.AddMachine(machine);
-            dict.AddItem(datItem, machineIndex, sourceIndex, statsOnly: false);
+            item.MachineIndex = machineIndex;
+
+            dict.AddItem(item, statsOnly: false);
 
             dict.RemoveBucket("game-1");
 
@@ -546,7 +632,7 @@ namespace SabreTools.Metadata.DatFiles.Test
 
             Machine machine = new Machine { Name = "game-1" };
 
-            DatItem datItem = new Rom
+            DatItem item = new Rom
             {
                 Name = "rom-1",
                 Size = 1024,
@@ -555,9 +641,13 @@ namespace SabreTools.Metadata.DatFiles.Test
             };
 
             var dict = new ItemDatabase();
+
             long sourceIndex = dict.AddSource(source);
+            item.SourceIndex = sourceIndex;
             long machineIndex = dict.AddMachine(machine);
-            long itemIndex = dict.AddItem(datItem, machineIndex, sourceIndex, statsOnly: false);
+            item.MachineIndex = machineIndex;
+
+            long itemIndex = dict.AddItem(item, statsOnly: false);
 
             dict.RemoveItem(itemIndex);
 
@@ -632,13 +722,25 @@ namespace SabreTools.Metadata.DatFiles.Test
 
             // Setup the dictionary
             var dict = new ItemDatabase();
+
             long sourceIndex = dict.AddSource(source);
+            rom1.SourceIndex = sourceIndex;
+            rom2.SourceIndex = sourceIndex;
+            rom3.SourceIndex = sourceIndex;
+            rom4.SourceIndex = sourceIndex;
+
             long machine1Index = dict.AddMachine(machine1);
+            rom1.MachineIndex = machine1Index;
+            rom2.MachineIndex = machine1Index;
+
             long machine2Index = dict.AddMachine(machine2);
-            dict.AddItem(rom1, machine1Index, sourceIndex, statsOnly: false);
-            dict.AddItem(rom2, machine1Index, sourceIndex, statsOnly: false);
-            dict.AddItem(rom3, machine2Index, sourceIndex, statsOnly: false);
-            dict.AddItem(rom4, machine2Index, sourceIndex, statsOnly: false);
+            rom3.MachineIndex = machine2Index;
+            rom4.MachineIndex = machine2Index;
+
+            dict.AddItem(rom1, statsOnly: false);
+            dict.AddItem(rom2, statsOnly: false);
+            dict.AddItem(rom3, statsOnly: false);
+            dict.AddItem(rom4, statsOnly: false);
 
             dict.BucketBy(itemKey);
             Assert.Equal(expected, dict.SortedKeys.Length);
@@ -672,10 +774,17 @@ namespace SabreTools.Metadata.DatFiles.Test
 
             // Setup the dictionary
             var dict = new ItemDatabase();
+
             long sourceIndex = dict.AddSource(source);
+            rom1.SourceIndex = sourceIndex;
+            rom2.SourceIndex = sourceIndex;
+
             long machineIndex = dict.AddMachine(machine);
-            dict.AddItem(rom1, machineIndex, sourceIndex, statsOnly: false);
-            dict.AddItem(rom2, machineIndex, sourceIndex, statsOnly: false);
+            rom1.MachineIndex = machineIndex;
+            rom2.MachineIndex = machineIndex;
+
+            dict.AddItem(rom1, statsOnly: false);
+            dict.AddItem(rom2, statsOnly: false);
 
             dict.Deduplicate();
             Assert.Equal(1, dict.DatStatistics.TotalCount);
@@ -732,18 +841,22 @@ namespace SabreTools.Metadata.DatFiles.Test
 
             var romA = new Rom
             {
+                SourceIndex = sourceAIndex,
+                MachineIndex = machineAIndex,
                 Name = "same-name",
                 CRC32 = "BEEFDEAD"
             };
-            long romAIndex = dict.AddItem(romA, machineAIndex, sourceAIndex);
+            long romAIndex = dict.AddItemInternal(romA);
             KeyValuePair<long, DatItem>? romAPair = new KeyValuePair<long, DatItem>(romAIndex, romA);
 
             var romB = new Rom
             {
+                SourceIndex = sourceBIndex,
+                MachineIndex = machineBIndex,
                 Name = "same-name",
                 CRC32 = "DEADBEEF"
             };
-            long romBIndex = dict.AddItem(romB, machineBIndex, sourceBIndex);
+            long romBIndex = dict.AddItemInternal(romB);
             KeyValuePair<long, DatItem>? romBPair = new KeyValuePair<long, DatItem>(romBIndex, romB);
 
             var actual = dict.GetDuplicateStatus(romAPair, sourceA, romBPair, sourceB);
@@ -768,18 +881,22 @@ namespace SabreTools.Metadata.DatFiles.Test
 
             var romA = new Rom
             {
+                SourceIndex = sourceAIndex,
+                MachineIndex = machineAIndex,
                 Name = "same-name",
                 CRC32 = "DEADBEEF"
             };
-            long romAIndex = dict.AddItem(romA, machineAIndex, sourceAIndex);
+            long romAIndex = dict.AddItemInternal(romA);
             KeyValuePair<long, DatItem>? romAPair = new KeyValuePair<long, DatItem>(romAIndex, romA);
 
             var romB = new Rom
             {
+                SourceIndex = sourceBIndex,
+                MachineIndex = machineBIndex,
                 Name = "same-name",
                 CRC32 = "DEADBEEF"
             };
-            long romBIndex = dict.AddItem(romB, machineBIndex, sourceBIndex);
+            long romBIndex = dict.AddItemInternal(romB);
             KeyValuePair<long, DatItem>? romBPair = new KeyValuePair<long, DatItem>(romBIndex, romB);
 
             var actual = dict.GetDuplicateStatus(romAPair, sourceA, romBPair, sourceB);
@@ -804,18 +921,22 @@ namespace SabreTools.Metadata.DatFiles.Test
 
             var romA = new Rom
             {
+                SourceIndex = sourceAIndex,
+                MachineIndex = machineAIndex,
                 Name = "same-name",
                 CRC32 = "DEADBEEF"
             };
-            long romAIndex = dict.AddItem(romA, machineAIndex, sourceAIndex);
+            long romAIndex = dict.AddItemInternal(romA);
             KeyValuePair<long, DatItem>? romAPair = new KeyValuePair<long, DatItem>(romAIndex, romA);
 
             var romB = new Rom
             {
+                SourceIndex = sourceBIndex,
+                MachineIndex = machineBIndex,
                 Name = "same-name",
                 CRC32 = "DEADBEEF"
             };
-            long romBIndex = dict.AddItem(romB, machineBIndex, sourceBIndex);
+            long romBIndex = dict.AddItemInternal(romB);
             KeyValuePair<long, DatItem>? romBPair = new KeyValuePair<long, DatItem>(romBIndex, romB);
 
             var actual = dict.GetDuplicateStatus(romAPair, sourceA, romBPair, sourceB);
@@ -840,18 +961,22 @@ namespace SabreTools.Metadata.DatFiles.Test
 
             var romA = new Rom
             {
+                SourceIndex = sourceAIndex,
+                MachineIndex = machineAIndex,
                 Name = "same-name",
                 CRC32 = "DEADBEEF"
             };
-            long romAIndex = dict.AddItem(romA, machineAIndex, sourceAIndex);
+            long romAIndex = dict.AddItemInternal(romA);
             KeyValuePair<long, DatItem>? romAPair = new KeyValuePair<long, DatItem>(romAIndex, romA);
 
             var romB = new Rom
             {
+                SourceIndex = sourceBIndex,
+                MachineIndex = machineBIndex,
                 Name = "same-name",
                 CRC32 = "DEADBEEF"
             };
-            long romBIndex = dict.AddItem(romB, machineBIndex, sourceBIndex);
+            long romBIndex = dict.AddItemInternal(romB);
             KeyValuePair<long, DatItem>? romBPair = new KeyValuePair<long, DatItem>(romBIndex, romB);
 
             var actual = dict.GetDuplicateStatus(romAPair, sourceA, romBPair, sourceB);
@@ -876,18 +1001,22 @@ namespace SabreTools.Metadata.DatFiles.Test
 
             var romA = new Rom
             {
+                SourceIndex = sourceAIndex,
+                MachineIndex = machineAIndex,
                 Name = "same-name",
                 CRC32 = "DEADBEEF"
             };
-            long romAIndex = dict.AddItem(romA, machineAIndex, sourceAIndex);
+            long romAIndex = dict.AddItemInternal(romA);
             KeyValuePair<long, DatItem>? romAPair = new KeyValuePair<long, DatItem>(romAIndex, romA);
 
             var romB = new Rom
             {
+                SourceIndex = sourceBIndex,
+                MachineIndex = machineBIndex,
                 Name = "same-name",
                 CRC32 = "DEADBEEF"
             };
-            long romBIndex = dict.AddItem(romB, machineBIndex, sourceBIndex);
+            long romBIndex = dict.AddItemInternal(romB);
             KeyValuePair<long, DatItem>? romBPair = new KeyValuePair<long, DatItem>(romBIndex, romB);
 
             var actual = dict.GetDuplicateStatus(romAPair, sourceA, romBPair, sourceB);
@@ -924,10 +1053,17 @@ namespace SabreTools.Metadata.DatFiles.Test
 
             // Setup the dictionary
             var dict = new ItemDatabase();
+
             long sourceIndex = dict.AddSource(source);
+            rom1.SourceIndex = sourceIndex;
+            rom2.SourceIndex = sourceIndex;
+
             long machineIndex = dict.AddMachine(machine);
-            dict.AddItem(rom1, machineIndex, sourceIndex, statsOnly: false);
-            dict.AddItem(rom2, machineIndex, sourceIndex, statsOnly: false);
+            rom1.MachineIndex = machineIndex;
+            rom2.MachineIndex = machineIndex;
+
+            dict.AddItem(rom1, statsOnly: false);
+            dict.AddItem(rom2, statsOnly: false);
 
             // Setup the test item
             DatItem rom = new Rom
@@ -971,10 +1107,17 @@ namespace SabreTools.Metadata.DatFiles.Test
 
             // Setup the dictionary
             var dict = new ItemDatabase();
+
             long sourceIndex = dict.AddSource(source);
+            rom1.SourceIndex = sourceIndex;
+            rom2.SourceIndex = sourceIndex;
+
             long machineIndex = dict.AddMachine(machine);
-            dict.AddItem(rom1, machineIndex, sourceIndex, statsOnly: false);
-            dict.AddItem(rom2, machineIndex, sourceIndex, statsOnly: false);
+            rom1.MachineIndex = machineIndex;
+            rom2.MachineIndex = machineIndex;
+
+            dict.AddItem(rom1, statsOnly: false);
+            dict.AddItem(rom2, statsOnly: false);
 
             // Setup the test item
             DatItem rom = new Rom
@@ -1007,9 +1150,13 @@ namespace SabreTools.Metadata.DatFiles.Test
             };
 
             var dict = new ItemDatabase();
+
             long sourceIndex = dict.AddSource(source);
+            item.SourceIndex = sourceIndex;
             long machineIndex = dict.AddMachine(machine);
-            _ = dict.AddItem(item, machineIndex, sourceIndex, statsOnly: false);
+            item.MachineIndex = machineIndex;
+
+            _ = dict.AddItem(item, statsOnly: false);
 
             Assert.Equal(1, dict.DatStatistics.TotalCount);
             Assert.Equal(1, dict.DatStatistics.GetItemCount(Data.Models.Metadata.ItemType.Rom));
diff --git a/SabreTools.Metadata.DatFiles/DatFile.Splitting.cs b/SabreTools.Metadata.DatFiles/DatFile.Splitting.cs
index 1066a97c..f195e46d 100644
--- a/SabreTools.Metadata.DatFiles/DatFile.Splitting.cs
+++ b/SabreTools.Metadata.DatFiles/DatFile.Splitting.cs
@@ -451,7 +451,8 @@ namespace SabreTools.Metadata.DatFiles
                             .Contains(mergeTag))
                         {
                             item.Value.MachineIndex = cloneOfMachine.Key;
-                            ItemsDB.AddItem(item.Value, cloneOfMachine.Key, source.Key);
+                            item.Value.SourceIndex = source.Key;
+                            ItemsDB.AddItemInternal(item.Value);
                         }
 
                         // If there is no merge tag, add to parent
@@ -461,7 +462,8 @@ namespace SabreTools.Metadata.DatFiles
                             .Contains(disk.Name))
                         {
                             item.Value.MachineIndex = cloneOfMachine.Key;
-                            ItemsDB.AddItem(item.Value, cloneOfMachine.Key, source.Key);
+                            item.Value.SourceIndex = source.Key;
+                            ItemsDB.AddItemInternal(item.Value);
                         }
                     }
 
@@ -489,7 +491,8 @@ namespace SabreTools.Metadata.DatFiles
                                 rom.Name = $"{machineName}\\{rom.Name}";
 
                             item.Value.MachineIndex = cloneOfMachine.Key;
-                            ItemsDB.AddItem(item.Value, cloneOfMachine.Key, source.Key);
+                            item.Value.SourceIndex = source.Key;
+                            ItemsDB.AddItemInternal(item.Value);
                         }
 
                         // If the parent doesn't already contain this item, add to subfolder of parent
@@ -499,7 +502,8 @@ namespace SabreTools.Metadata.DatFiles
                                 rom.Name = $"{machineName}\\{rom.Name}";
 
                             item.Value.MachineIndex = cloneOfMachine.Key;
-                            ItemsDB.AddItem(item.Value, cloneOfMachine.Key, source.Key);
+                            item.Value.SourceIndex = source.Key;
+                            ItemsDB.AddItemInternal(item.Value);
                         }
                     }
 
@@ -510,7 +514,8 @@ namespace SabreTools.Metadata.DatFiles
                             item.Value.SetName($"{machineName}\\{item.Value.GetName()}");
 
                         item.Value.MachineIndex = cloneOfMachine.Key;
-                        ItemsDB.AddItem(item.Value, cloneOfMachine.Key, source.Key);
+                        item.Value.SourceIndex = source.Key;
+                        ItemsDB.AddItemInternal(item.Value);
                     }
 
                     // Remove the current item
@@ -609,10 +614,13 @@ namespace SabreTools.Metadata.DatFiles
                 foreach (var item in parentItems)
                 {
                     DatItem datItem = (DatItem)item.Value.Clone();
+                    datItem.MachineIndex = machine.Key;
+                    datItem.SourceIndex = source.Key;
+
                     if (items.Values.Any(i => i.GetName()?.ToLowerInvariant() == datItem.GetName()?.ToLowerInvariant())
                         && items.Values.Any(i => i == datItem))
                     {
-                        ItemsDB.AddItem(datItem, machine.Key, source.Key);
+                        ItemsDB.AddItemInternal(datItem);
                     }
                 }
 
@@ -874,7 +882,10 @@ namespace SabreTools.Metadata.DatFiles
 
                                 // Clone the item and then add it
                                 DatItem datItem = (DatItem)item.Clone();
-                                ItemsDB.AddItem(datItem, machine.Key, source.Key);
+                                datItem.MachineIndex = machine.Key;
+                                datItem.SourceIndex = source.Key;
+
+                                ItemsDB.AddItemInternal(datItem);
                             }
                         }
                     }
@@ -884,8 +895,14 @@ namespace SabreTools.Metadata.DatFiles
                     {
                         if (!deviceReferences.Contains(deviceReference))
                         {
-                            var deviceRef = new DeviceRef { Name = deviceReference };
-                            ItemsDB.AddItem(deviceRef, machine.Key, source.Key);
+                            var deviceRef = new DeviceRef
+                            {
+                                MachineIndex = machine.Key,
+                                SourceIndex = source.Key,
+                                Name = deviceReference,
+                            };
+
+                            ItemsDB.AddItemInternal(deviceRef);
                         }
                     }
                 }
@@ -929,7 +946,10 @@ namespace SabreTools.Metadata.DatFiles
 
                                 // Clone the item and then add it
                                 DatItem datItem = (DatItem)item.Clone();
-                                ItemsDB.AddItem(datItem, machine.Key, source.Key);
+                                datItem.MachineIndex = machine.Key;
+                                datItem.SourceIndex = source.Key;
+
+                                ItemsDB.AddItemInternal(datItem);
                             }
                         }
                     }
@@ -939,11 +959,21 @@ namespace SabreTools.Metadata.DatFiles
                     {
                         if (!slotOptions.Contains(slotOption))
                         {
-                            var slotOptionItem = new SlotOption { DevName = slotOption };
+                            var slotOptionItem = new SlotOption
+                            {
+                                MachineIndex = machine.Key,
+                                SourceIndex = source.Key,
+                                DevName = slotOption,
+                            };
 
-                            var slotItem = new Slot { SlotOption = [slotOptionItem] };
+                            var slotItem = new Slot
+                            {
+                                MachineIndex = machine.Key,
+                                SourceIndex = source.Key,
+                                SlotOption = [slotOptionItem],
+                            };
 
-                            ItemsDB.AddItem(slotItem, machine.Key, source.Key);
+                            ItemsDB.AddItemInternal(slotItem);
                         }
                     }
                 }
@@ -1027,10 +1057,13 @@ namespace SabreTools.Metadata.DatFiles
                 foreach (var item in parentItems)
                 {
                     DatItem datItem = (DatItem)item.Value.Clone();
+                    datItem.MachineIndex = machine.Key;
+                    datItem.SourceIndex = source.Key;
+
                     if (items.Any(i => i.Value.GetName() == datItem.GetName())
                         && items.Any(i => i.Value == datItem))
                     {
-                        ItemsDB.AddItem(datItem, machine.Key, source.Key);
+                        ItemsDB.AddItemInternal(datItem);
                     }
                 }
             }
diff --git a/SabreTools.Metadata.DatFiles/DatFile.cs b/SabreTools.Metadata.DatFiles/DatFile.cs
index 303aa7c9..9eab8315 100644
--- a/SabreTools.Metadata.DatFiles/DatFile.cs
+++ b/SabreTools.Metadata.DatFiles/DatFile.cs
@@ -227,7 +227,11 @@ namespace SabreTools.Metadata.DatFiles
         /// <returns>The index for the added item, -1 on error</returns>
         public long AddItemDB(DatItem item, long machineIndex, long sourceIndex, bool statsOnly)
         {
-            return ItemsDB.AddItem(item, machineIndex, sourceIndex, statsOnly);
+            // TODO: Have the callers of this method set them instead
+            item.MachineIndex = machineIndex;
+            item.SourceIndex = sourceIndex;
+
+            return ItemsDB.AddItem(item, statsOnly);
         }
 
         /// <summary>
diff --git a/SabreTools.Metadata.DatFiles/ItemDatabase.cs b/SabreTools.Metadata.DatFiles/ItemDatabase.cs
index c6f30461..9a6261fb 100644
--- a/SabreTools.Metadata.DatFiles/ItemDatabase.cs
+++ b/SabreTools.Metadata.DatFiles/ItemDatabase.cs
@@ -157,11 +157,9 @@ namespace SabreTools.Metadata.DatFiles
         /// Add a DatItem to the dictionary after validation
         /// </summary>
         /// <param name="item">Item data to validate</param>
-        /// <param name="machineIndex">Index of the machine related to the item</param>
-        /// <param name="sourceIndex">Index of the source related to the item</param>
         /// <param name="statsOnly">True to only add item statistics while parsing, false otherwise</param>
         /// <returns>The index for the added item, -1 on error</returns>
-        public long AddItem(DatItem item, long machineIndex, long sourceIndex, bool statsOnly)
+        public long AddItem(DatItem item, bool statsOnly)
         {
             // If we have a Disk, File, Media, or Rom, clean the hash data
             if (item is Disk disk)
@@ -261,7 +259,7 @@ namespace SabreTools.Metadata.DatFiles
             }
             else
             {
-                return AddItem(item, machineIndex, sourceIndex);
+                return AddItemInternal(item);
             }
         }
 
@@ -517,12 +515,8 @@ namespace SabreTools.Metadata.DatFiles
         /// <summary>
         /// Add an item, returning the insert index
         /// </summary>
-        internal long AddItem(DatItem item, long machineIndex, long sourceIndex)
+        internal long AddItemInternal(DatItem item)
         {
-            // Add the machine and source index
-            item.MachineIndex = machineIndex;
-            item.SourceIndex = sourceIndex;
-
 #if NET40_OR_GREATER || NETCOREAPP || NETSTANDARD2_0_OR_GREATER
             // Add the item with a new index
             long index = Interlocked.Increment(ref _itemIndex) - 1;
@@ -586,20 +580,9 @@ namespace SabreTools.Metadata.DatFiles
                 Sort(ref sortedList, false);
                 sortedList = Merge(sortedList);
 
-                // Get all existing mappings
-                List<ItemMappings> currentMappings = sortedList.ConvertAll(item =>
-                {
-                    return new ItemMappings(
-                        item.Value,
-                        GetMachineForItem(item.Key).Key,
-                        GetSourceForItem(item.Key).Key
-                    );
-                });
-
                 // Add the list back to the dictionary
                 RemoveBucket(key);
-                currentMappings.ForEach(map =>
-                    AddItem(map.Item, map.MachineId, map.SourceId));
+                sortedList.ForEach(item => AddItemInternal(item.Value));
 #if NET40_OR_GREATER || NETCOREAPP || NETSTANDARD2_0_OR_GREATER
             });
 #else
diff --git a/SabreTools.Metadata.DatFiles/ItemMappings.cs b/SabreTools.Metadata.DatFiles/ItemMappings.cs
deleted file mode 100644
index 0ccfcdfe..00000000
--- a/SabreTools.Metadata.DatFiles/ItemMappings.cs
+++ /dev/null
@@ -1,12 +0,0 @@
-namespace SabreTools.Metadata.DatFiles
-{
-    /// <summary>
-    /// Class used during deduplication
-    /// </summary>
-    public struct ItemMappings(DatItems.DatItem item, long machineId, long sourceId)
-    {
-        public DatItems.DatItem Item = item;
-        public long MachineId = machineId;
-        public long SourceId = sourceId;
-    }
-}