8 1/4 or 8 3/4 rear end

The 7.25 will put up with a 318/ auto trans, for a good long time, in a small-tub car; but it will not put up with peg-legging for long.
So if your 7.25 has the right ratio in it, I would just put a Sure-Grip in it.
But if you have to buy gears too, then not.