M-6049-X303. Complete Head (64cc chamber). The Ford Racing GT-40 "P" high-flow cast iron cylinder heads flow 185 cfm of air right out of the box, giving your small block Ford greater power potential. Designed for Ford 289-351W engines, the complete assemblies have 60cc combustion chambers, 1.84 in. intake/1.46 in. exhaust valves, and work with stock or aftermarket intakes, rockers, and valve covers. NOTE: specs & photos can vary