273 / 318 Exhaust Manifold Question

George Jets said

... Here is the thing with your 273 and heads. Intake manifold bolts go in at a different angle than the newer aluminum intakes and newer 318 heads.. Then you have port runner size most of them large port. So then you get a miss match at your head ports...

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This information is incorrect. He has 920 heads from 66 and 67 so they use the standard intake bolt pattern. They are the best "as cast" flowing small port heads, including 302 heads. They are closed chamber heads. The Performer is also a small port intake.