I like Fel-pro neoprene (rubber) valve cover gaskets. Tell the parts guy to look up a 67 Barracuda with a 273 4 bbl. Since they have the adjustable rocker arms, they will list the neoprene re-usable ones for it. They are also re-usable if you can get them to seal without any sealer (permatex, gaskacinch, etc).