Will 318, 340 or 360 heads fit on a 273?

nm9stheham said

675 is the last 3 digits in the casting number on the head for the later open chamber 2 BBL heads on 273's. They have chamber volumes that are typicaly around 68 cc's.

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I thought -675 open chamber heads didn't come around until 68

OP's 1966 stock 273 should have -920 closed chamber heads,no? Which IIRC are speced on 273s, closer to 57/60cc,no?