I run trx based diffs in my GA cases - using flm cups and a modded ring gear that upgrades the stock 2mm screws to 3mm screws. I have a few sets of UE 6 and 8 spdyer diffs and they look to big to fit in GA cases, but I've never tried.

I went over to UE and found a thread that says the 6 spyder diffs will not fit stock diff cases. Logically if they won't fit stock cases, then it would make sense that they won't fit GA diff cases either.