Bob, seriously, I see such-and-such compression ratio pistons listed all the time. Those figures mean nothing when figuring compression ratio and you must know the correct c.r. in order to choose the correct cam. Here's the info needed.
bore
stroke
combustion chamber cc's
bore and compressed thickness of the head gasket
piston deck
piston crown configuration, dome, flat-top, flat-top with valve notches, dish, dish cc's
So, you see, 10 1/2 to 1 pistons means nothing