i got an '87 with a 231 amc t-case (stock) i got the rear drive shaft i need and the windows going good except the motor that took a crap on me earlier.. anyhow

what sort of t-case upgrade can i do?

depends on what kind of 4 wheeling your going to do, if your not going to do real hard core stuff your xfercase if fine in stock form, if your going to bigger tire which mean bigger lift above 3 inches, you need to do a slip yoke eliminator kit, which you can upgrade to the 31 spline main shaft.

Oh by the way, its not a AMC transfer case, its a New Process, AMC did not make transfer cases