Im no stranger to the fact either. I built my Slant 6 70 Dart with an 8.75 rear end. My slant physically broke the gears in the 7 1/4. I didn't want to be stranded again so I slipped in a 70 B-Body 8.75. Freshened up the 3.23s and I was off again. My slant was notoriously a torque monster and breaking stuff left and right.