[James]

Originally Posted by Funky61

All 305A,B,C,D,E, 351C,E,M, 379, 401, 401M, 432, 478, 478M V6 engines, other than bore sizes all share the same basic block architecture and dimensions therefore cylinder heads, corresponding intake and exhaust manifolds, valve covers, pushrod covers, distributors, water pump-timing cover housings along with corresponding water manifolds, camshafts, gear drives on 401 to 478, chain drives from 305 to 379, crankshafts other than 73 to 74 478M, oil pans, oil filter housings are INTERCHANGEABLE !
Pete Chronis

The only thing that I know that is not interchangeable is mixing the magnum head, intake or exhaust manifolds with the smaller (305) heads. The ports on the magnum is a lot larger and will not seal if mixed. I think there is a different in the oil pump mounting bolt too (5/16" vs 3/8").

Use the magnum heads with magnum manifolds and smaller heads with the smaller manifolds.