He's looking at almost 420 cubic inches - those heads won't hurt. But I would say that a set of 243's would get him to his goal as well. He should be able to hit his goal, but I don't think this will be a friendly car on the street with a stick - but sometimes, unfriendly is more funYou won't have enough motor to notice a horsepower difference between the 823 heads on the 6.2 and the AFR heads. But with that cam your dynamic compression would make the static compression manageable. Are you going with an MSD ignition module?