Good point I hadn't thought about that yet. I am waiting to get the all clear on the block before I buy pistons and rings. The piston selection is pretty limited to either reproduction stock gm or mercruiser units. The GM slugs only get 7.5 ish compression (depending on head combustion chamber of course, limited there to), but the Mercruiser pistons are closer to 8.5 to 1. Not great but better than the GM style pistons. The guy who is doing my head has a line of custom forged pistons that can be a little over 9.5 to 1 depending on the head. Basically a zero deck design, no dish in the top of the piston. However he only sells them in 40 over, since I am 60 over that isn't an option. He also gets 600$ a set, ouch! But he is the only game in town on the forged pistons!