ya i would suggest a new rear end, the mazda ones like to blow up spider gears, u can do any rear end u want, sotra... if u want to keep the six bolt pattern, u can go with a 4 runner rear end and the make limited slip for them, i have seen ranger rear ends mustangs and toyota 2wd pick ups lots of times
I just bought a '89 thunderbird with a 302 in it. the motor runs, but the tranny is shot. I'm just using the rear end from the t-bird (same width as the mazda but beefier). only problem is it's 4 lug. but I heard you can throw in ranger axles to switch 5 lug. I don't know yet though