Is a 7.25 rear strong enough?

My 7 .25 died behind a mild 318 with a 4 barrel. The 273 never hurt it. After replacing the 7.25 with an 8.75 I took out the 904.
A friend had one with a slant six and a 3 speed. He would roll down a hill backwards dump the clutch with the pedal to the floor in 1st. Did some pretty smoky burnouts this way. He never killed the rear but should have.
I knew a couple other people who's 7.25 s died. I think if they were driven normal they would have lasted longer. But where is the fun in driving normal.