MG - vERY SORRY THIS THREAD SLIPPED THROUGH THE CRACKS FOR US.
geez sorry about the caps too.
The 12 bolt olds with the parts you bought will hold up great even with what you think is high HP and Torque.
Factory Big Blocks had 500 ft lbs. from 2800 RPM which is TONS of torque.
Just be sure if you or some one else is setting up the rear...they pay attention to the small details . Getting the ring and pinion set correctly will be the BIGGEST reason the rear holds or DOES NOT HOLD... Then be sure you run the gears through the break in procedure of heat up and cool down cycles.1st run 5 min around the block and a 30-45min cool down completely.
2nd run 10 min around the blocks in the neighborhood again and a 1 hour shut down completely to ambient outside temperature.
(This is quenching the gears in the oil bath and each time you heat and cool you are hardening the gears) Remember the gear bath is only 1/2 full and the reason for so many heat and cool cycles to try and get the complete circumference of the ring hardened properly.
do about 2-3 more cycles and then you can hit it and see how the car performances - again the more small runs you do with cool down will complete the hardening and build confidence in your new rebuilt rear.
J D RAce