Interesting point Michael. The piston to bore clearance spec was .007, which is a lot, generally speaking. My new custom pistons are spec'd at .0035, for instance.
I'm betting that back in the day they still used the same "basic size" piston for the same "basic bore", thus piston clearance could have varied per motor by several thousandths? It's possible!
Perhaps THAT is why some motors just naturally seem to run stronger than others, even true today. Some spec race divisions demand "exact" factory specs for the motors. I've heard rumors that some teams "with connections" go through a ton of new "parts" searching for the "perfect" valve, or piston or head or whatever. No machineing allowed, so you go through the "bin" and find those perfect parts to "blue print" your motor.
Reminds of a Darryl Waltrip comment years ago. He (or his team members) would hang out by the Goodyear truck that brought the tires in. There they would carefully go through them and pick out those "perfect" tires. This gave them a measurable advantage on the track and other teams knew those boys "were up to something", but cound not figure out WHAT! When it was discovered, NASCAR stopped that and tire distribution was closely watched!
