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Thing is, around 60cc chambers allow a pretty good cr. However, if the combustion chamber design follows the head gasket profile, 60cc chambers turn out pretty shallow, with the corresponding reduction in breathing. So, if the combustion chamber shape is altered to become narrower between the inlet valve to cylinder, [which is where we want to enhance breathing], it could be deepened, giving the same 60 cc volume. The exhaust side of combustion chamber, because it's not relying on atmospheric pressure for flow, rather, the positive displacement that occurs from the rising piston, does not need the same flow enhancements.
if you look at the photos in the first post in this link;
https://www.fordbarn.com/forum/showthread.php?t=303408 you might see sort of what I'm on about. One combustion chamber follows the head gasket profile, the other is longer and narrower, and favours the inlet charge. Both are approximately the same volume, but I'll bet flow is different in each head. So, from a performance point, which head is of the better design?