My stock, 50K mile,T-56 takes 575rwhp just fine. (3,800lb GTO) The problem is gonna be the clutch lol, a good strong clutch isn't cheap. I will say the OEM LS7 clutch held up pretty well to my 470rwhp but I didn't want to chance it when I added more power.
How much does a RCSB weigh?

Either way, Finish Line Transmission is the place to call.