Power limits of the 7 1/4 suregrip?

I'd becareful with that rear, even more so on that description.
Replace it? Yes, agreed.
I would look into a 8-1/4 or the 8-3/4. The later is more expensive. The 1/4 rear can take a decent amount of power. If you plan on more than 400 "race" hp, I'd go up in size to the 3/4. Otherwise, you'll be fine.
The A body 3/4 rear is mostly found with a small bolt pattern. (5 on a 4 circle) Which makes rim choices limited or custom ordered.
The 1/4 rear is a (Mostly allways I believe) a 5 on a 4-1/2 circle. Which takes rim choices into a bigger book of choices.
Food for thought, I scored a 8-1/4 with a suregrip and 3.21's for $200. I don't know how that compares to the rest of you, but a clean up and bolt in was just fine by me. There also not exactly easy to come by around here.