72 Buick Stage 1 G.S. had a net rating of 270 h.p. and the '71 had a gross rating of 340 h.p. and was the exact same engine.
I got a well tuned, stone stock 72 Stage1 to go 13.59 with a mandrel bent 2&1/2" exhaust system. Car was just under 4200lbs with driver. This was a perfect air, perfect track condition day. Most other days it was a 13.70's-13.8x's car. Total crap muggy air, it was lucky to crack 13.99, and would settle into the 14.0x-14.teens. That doesn't answer your HP question, but it shows a low compression car will run pretty darn good. Edit>>>>FWIW, Same engine rebuilt at a later date, std bore, put in a set of high compression 70 GM pistons, car ended up running 13.30. I wouldn't get too concerned with a power drop going from a 70, to a 71-72, I highly doubt you'll notice, plus you can run cheap 87 octane in a 71-72.
I think the price has dropped to around 53K. When I saw the video of the car being driven I thought it was odd how they did not "get on it" like they do to almost all their other cars.
I just saw a video of theirs showing a 70 455 GTO wrong motor no underside pics possible incorrect color asking 55? I thought that was a ton.
I would love to get my Stage 1 GS! When I askd these guys specific questions it was like "Church Mice" ! What are they hiding???