If the block is being blueprinted, you will want to stay below .520 advertised lift. You lose about .019" because of the pushrod angle of the block. Normally the "10.5:1" pistons actually are closer to 9.5:1 and nowhere near the valves. But you will want to be careful if you're using a modern high-rate-of-lift cam. IMO, you'd do better to get a better and lighter piston with deeper valve pockets if this is a full rebuild.