99SC42 -- if you found that an LS430 diff bolted right in that's a new one on me and I don't think it's common knowledge for SC, GS and Supra MKIV owners. Owners should be made more aware if it's the same diff pumpkin down to the mounting points.
Vrank -- This is true. The IS350 and IS-F rear diffs look VERY similar to the SC/GS/MKIV 200mm rear differentials. There was an IS-F diff thread elsewhere on CL where this was discussed but it did look as if only the ears were cast in the same location. I can't remember specifically but there were slightly different mounting points on the IS350/IS-F castings even though they are probably internally the same 200mm design. Unless there are differences in pinion diameter and/or length it's very possible that the internals are swappable to a traditionally SC-compatible pumpkin. Don't hold me to that last speculation because I haven't confirmed or tried it but it would make sense Toyota would re-use most of their diff designs for certain applications. They did it using the MKIII/Cressida/IS300/IS250 diffs in the FR-S after all.
Last edited by KahnBB6; 08-01-14 at 02:28 PM.