273 head choice ?

Garrett Ellison said

I don’t know how the the early 234 head ports compare to the 234 industrial 318 heads, but the industrial head ports look immeasurably better than 302 casting heads. My machinist confirmed that he can block the water crossover on them. They look like some 11/32 stem 1.82 (305 Chevy) /1.60 exhaust stainless valves and some porting could make them very good for a 273.

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Yeah, I would run the 920 or the industrial heads over the 302 castings. On my engine I blocked the water crossover with 0.010" shim stock and rtv and used the thicker felpro 1243 gasket to take up the variance on the gasket face and it sealed up well.
To the OP I'm not saying the 302s won't run well but they would probably want a bit of work done. if your set on using them check out moparofficials thread - some good info there.