You have several options.
First is pick up a set of closed or open chambered oval port stock heads that are good cores and rebuild.
Cheapest is just put new stock small valves back in and a good three angle valve job and just a hand bowl job and runner casting flash clean up.
-215's or 206 type are good starters for closed heads. -781's and -049's good open heads.
Next, totally rebuild same heads but with big valves, big spring seats and guides cut down for good seals. Install hardened seats and maybe new bronze guides.
Last, buy a set of new cast-iron Merlin oval heads and install needed stuff into them! Also do a hand bowl clean up and runner casting flash removal.
But one thing for sure is to match your compression ratio to piston dome height, quench or deck height, headgasket thickness and finally cc of combustion chamber being used.
Set CR. about 9.5 to 1 for pump gas and slightly above 10 to 1 CR. if you want to run a bigger cam that will bleed off some compression so that you can still burn pump gas!!!
Check out Competition Products b/c they offer good value for the money. Heck, you might even consider a set of Canfield aluminum heads for the money AND weight savings!!!
I went with the Merlins like above and bought most of the needed stuff from C/P!! But this was before I knew about the inexpensive Canfield's!!!
Good luck with your project and let us know what you do. pdq67
