I have a '70 olds 455 block- performer intake, forged pistons, compcams bumpstick and a bunch of other things. Unfortunately, the engine is not yet installed. It will be mated to a massaged ex GN / 442 T200-4R (upgraded with corvette clutches, high perf. bands etc.) The tranny is built to take 700 HP. The engine is built for torque, not max HP. I figure that I'll see 500-520 HP, 530-560 ft-lbs torque. The hang-up this year had to do with time and my decision not to carburate it as initially planned. I will be going to TBI, so I have a bit of work to do with the swap.
On another note, there is someone up here in Kelowna that is riving with a TBI 454 installed in his wagon- the car used to be in Vanc.
Hope it helps