When got my 67 Barracuda it had a later slant six radiator. It worked OK even when I put the 340 with the 70 up water pump in it. Unlike a correct pre 70 v-8 radiator, it was possible to find both upper and lower radiator hoses without resorting to flex hoses (never good for flow). However especially with A/C, in the summer stopped in traffic, thats when fan shroud and sufficient core will become important.