Hola Both the 331 and the 354 carried the hemi and the poly head. And the head can fit either size of engine. The 354 was used thru the '58 year. Rodger & Gabby Colo Spgs '47 De Soto Custom w/Fluid Drive & passenger door mounted swamp cooler '63 Le Baron w/F-Sweep trunk lid & std A/C '66 Le Baron w/dual A/C & reverbed AM/FM