Slant 6 Aluminum Performance Head

trying to follow this: to get 300+hp out of /6 w/aluminum head seems like making the wheel rounder. lots of folks would love it. problem,design n cost. what would be a fair price to pay?
nevermind design n cost to build. i have 3 /6's i drive. once asked my engine builder how much to rebuild he said, he never did 1. never had too. these /6's are almost indestructible. So would a aluminum head change all that?