Rear Brake Identification

So, I don't own any Mopar cars, nor have I ever worked on any, but I've got quite a problem and it pertains to some Mopar parts. I've got a 1973 AMC Javelin, and the guy I got it from put a 8 3/4" rear into it, and after a lot of brake work and guessing around, I've found out that he did some odd combination of AMC rear drum brake parts and Mopar parts. I've been trying to identify the backing plates and I know they are Mopar, but I can't distinguish if they are from an A body or B body or if they are 10" or 11". All I know is that the differential came from a 68 Roadrunner, so I can assume the brakes did as well. I'll try to post a few photos, and if anyone can point me in the right direction as to what drums, shoes, and other parts I should get I would greatly appreciate it.