I think the 906 casting was the best head for the 383, though I'm no expert. It's possible to get 300+ CFM out of one of those heads. 203 cc intake port and a 2.08 valve. I know of a 383 that made 620+ hp on the pump with more left in it.
Jared Jordan
7551 SS/BA
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Jared Jordan
9 B/SA
2024 Jeg's D7 All Star - Stock
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