Ummm, seems to me, v-e-r-y vague memory: there were several different heads for Poly engines, because of different applications, years and c.i.d. that in some cases had different cooling passages. Similar to interchanging some 361-440 parts. I'm thinking there were 25?, 273 [or close, and not the later 273LA] 313, 315, 318 [3 or 4 different ones] plus American, Canadian that were all Poly but not all the same, plus 'Industrial', truck, car & you name it. I'd swear Ron Reichert mentioned something about that?

The new heads should tell when the gaskets are matched to block & heads.