sborruso

Does anyone know if #18 heads which appear to be 59 vintage will fit in place of #23's 63-64 vintage.

59-59-59

I could of swore I read somewhere or saw it somewhere that the early 394 and late 394 heads will not work in stock form because the oil drain back holes do not line up. And the late and early 394 exhaust manifolds are totally different from each other as far as bolt pattern