The Hi-Po flywheel, identifiable by the orange paint mark, has the same casting number as a 2V/4V flywheel. Where it differs is offset balance (30.2 ounces versus 26.2 ounces), closer factory inspection for flaws, and Brinell hardness testing. You can actually run a Hi-Po flywheel on your 2V/4V engine as long as it is dynamic balanced with your rotating assembly. Ideally, you will have your Hi-Po Mustang's clutch pressure plate balanced with the flywheel, crank, rods, pistons, rings, and harmonic balancer. And, if you're really on top of the game, you will have the crank pulley balanced as well.