'65 Barracuda FS 273 4bbl 10.5 CR on pump gas in CA

Just measured the bore of the Fel-Pro gasket, and it measures 4.18", whereas the bore of the stock 273 is 3.625" per the FSM. Rock Auto shows this same gasket for a 318 and 273, it appears as though 273 head gaskets are not available. If the 318 gasket were used, that would reduce compression even more I would think.