I ran a stock case with a TCI planetary and guts in a 3500 lb door car with a 600+ HP SBC engine for the better part of 9 years and never hurt a case.
Had two dragsters, one 482 BBC and one 434 SBC with stock cases that worked fine.
I've built a s**t load of'em, including one behind a 496 BBC in a door car that have had zero case problems also. Ya have to realize that the load on the gearset is internal and there is very little radial jor axial force involved.
If that's what you got, then run it!