I doubt that any "blueprint" dimension exists for this. There were at least 3 different 235 heads from 54-62, all with different combustion volumes and other minor differances. The production tolerances during machining were probably fairly wide, as the 235 was never a close-tolerance performance engine.
As a machinist once said to me "heck, you could cut down this head with a hacksaw and you still wouldn't have valve-to-piston contact."
I've never even been able to find a listing for what the stock chamber volume is supposed to be, for any head casting #. Supposedly every .005" off the head removes about one CC from the volume. I'm having my '54 head CC'd, and its been shaved at least .040". I'll post the results here.
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