410'

I would ditch the factory heads and get some RHS heads. That way you'll have a quench combustion chamber and can run 10:1 or more compression on pump gas. With the open chamber factory heads they won't have quench and will be more prone to detonation so you'll be forced to run lower compression and make less power. Why dump all that cash into old obsolete heads when the RHS heads are readily available. Get Shady Dell to prep some of those up for you and bolt those on. It would be about the same cost as porting them old open chamber factory heads. I would also work with Ryan on the total combination. He will help you with getting the right combination of parts to meet your goals. He is very practical and down to earth and will provide outstanding expert advice; use it. Sell those x heads to someone hung up on a correct restoration type of car.