I don't know a lot about quench/squish other than what I've read.
My understanding is:
A relatively small (.032-.040") quench distance causes a turbulent "mixture motion" which in turn has a cooling effect to the combustion chamber. This deters/eliminates "hot spots" in the chamber and results in a more constant temperature. I think that's where the octane-tolerance comes from....no pre-ignition from said "hot spots". The turbulent motion also causes the fuel mixture to be more homogenous = more efficient burn.
Someone mentioned factory head gasket crushed thickness. Here's a photo of the old HO-Racing parts and specs book related to the gaskets.
I don't know if Royal Pontiac used the steel shim head gaskets as part of their Bobcat package to simply raise compression or if they actually knew about the benefits of a tight quench distance, but the gasket caused a positive effect for both.
I've taken apart MORE THAN 1 original '69 RA-IV engine that had the shim gaskets. Those engines appeared to have never been apart.
Don't forget how different fuel was back in the day. Benzene, Toluene, TEL were all a part of the old cocktail called fuel.
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