You'd need to mic em. Measure the outside of the pistons and the insides of the cylinders. The clymers manual lists the specs for what's considered an acceptable difference between the 2 but I don't know it off the top of my head. In addition, you want to check for either being out of round, or any obvious signs of wear - cracks, scratches, gouging. Check the ports for a rough edge, there shouldn't be any. Any excessive carbon build up should be removed.
Did I miss anything guys?