Lower compression 12.5:1-10.5:1 HELP!

[THEFED]

I have an interesting question. I've considered buying a 383 from a close friend of mine. It's pushing a 71 MONTE CARLO to 11.7 second ETS. He guesses 510 HP.

Regardless, he's running steel PRO ACTION heads, and a cam that's rouhly 250/26o @.050,.533/.553 lift. This is at 12:5-1 Compression.

What HP gain/loss would one expect from dropping compression to 9.5:1 or 10.5:1 or for pump gas, while replacing those heads with AFR 195's. ..keeping all else the same.

Any input would be super. Should I get it, swap cams, or what? He wants 1500 for the short block with cams and lifters . I know for a fact he spent about 2000 on machine work taking it to a 383, and has had 125 passes on it since. It's a clean, strong motor.

PS - That cam seems a little beefy for a 75/25 street/strip motor. I guess I could expect shi**y vaccum. he ran a vacuum reserve to help with that. anything else not advantageous about a cam like this?