So I changed the path of the project a bit, I bought a 1979 camaro and decided to use that, so I sold the AMC and the sweet explorer differential. I put the motor together this summer and dropped it in the camaro, so far it has done a 13.8@106mph. This winter I am going to install 3.42 gears (currently has 2.43), and a borg warner 4 speed transmission, hopefully that will help it go a bit better.
I just got my differential, its a 8.8" out of a '96 explorer. I got it from a junkyard for $300 with the driveshaft and delivery. It has 3.73 gears, limited slip, and disc brakes. Its approximatly the right width for a small body AMC, and already has the right wheel bolt pattern. The reason I got the driveshaft as well is because the pinion has a funny flange, so I will try to use the end of the old driveshaft