There is a lot of information missing here but with the flat top pistons and 500 HP goal, JohnRR is correct, the 84cc closed chamber heads would be better. The OOTB 60929 will support 500 HP.
Nothing wrong with bOb's answer. The Victor is much more of a race head and more expensive to set up with the offset rockers, having to buy retainers, locks, valve springs and all.
