It's possible you've got somebody's aftermarket heads like Dart, World Products, etc. How about posting a link to some pictures, or at least some casting numbers? Are they cast iron? The main difference in production heads was in the valve size and compression ratio, so the 4-barrel engines often got higher-performance heads than 2-barrel passenger car or truck engines.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
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