What can a 7 1/4 rear take???

I can say this, I had a 1970 Barracuda 318 2 barrel automatic car and it came from the factory/build sheet showed 7 1/4.
with a 7 1/4 and it had over 100.000 miles on it, just like my Valiant 7 1/4 first thing I did was replace the outer bearings and seals.