Didn't the factory engineers specify Dana 60 rear ends for cars approaching 500 ft/lbs torque , such as the six barrel cars ? . That would be the breaking point for the 8 3/4 setups, I would imagine.

No breakage here yet (489 case 8 3/4, 4.10) over 50 passes - another "advantage" of the smallblock - something to cheer about in one respect, I guess.