I actually kept digging and finally found this post from @
Jeff Lange:
http://www.ft86club.com/forums/showthread.php?p=302901
It looks like the carrier/differential assembly out of an IS300
is a direct fit for our cars. Good thing because I found a great deal on one at a local junkyard.

Now I just need to see if I can get the gear kit and required pinion seal through amayama or autofactory and I'm good to go!