Anyone knows about IRS diffs?

[vic]

Hello all, first post here. Somehow seemingly simple queston is so hard to find answer for, may be someone point me to right places (links). I'm doing a conversion of 4x4 to an electric and need differentials for IRS and IFS with short ratio - from about 5.7:1 to 6:1. Something smaller than monster Ford 9" - that one won't fit. Max torque it should handle is about 350 ft*lb. The smaller size - the better. Don't care what car it's coming from, it's extensively being modified anyway. The diff installed in front is really a rear diff, but should be with high pinion. Real diff is "normal" (low pinion). All I see is Ford and some Toyota diffs but mostly for solid axles. Ijust need complete 3rd members, that's it. Any pointers/sites are appreciated! Vic.