7 1/4?

I've embarked on my first A body build and my first build that's made for mostly racing, my Dart. I was going to start bracket racing with a mild (250-300 HP) 318 with a 904 or A-833 behind it and all I can get for a rear end locally that is a direct fit is a 7 1/4.

How long will this (or will it) hold up to the abuse?
Any suggested upgrades (beside 8 3/4 or 8/14)?

Thanks!