Stock high compression 340-Max cam lift?

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.