882 heads are notorious for being cracked!! Have them checked. As for the compression ratio with the 305 heads. In real life, Very, very, few factory chevy 350 blocks come close to pistons .020" down in the block. When I was in the machine shop business, the average was somewhere around .035" . That and a set of Re-ring type gaskets and you just may just touch 10-1 compression. This motor in a light body with a mild cam will run just fine on mid-grade gasolines. Now remember the only reason I reccommended the 305 heads was your limited budget. You will find that the 882's (if not cracked) will need a lot of guide and mill work. Just remember Horsepower costs money, how fast do you wanna go?