I am pretty sure it is the 65 cc for NHRA and 10.5. I've worked out the numbers before.... lessee....yep... 66 cc does it with 5 cc eyebrows and 1 cc in the crevice area.
And you can be almost 11:1 in an F or G stocker, which is a 73 340 car and I forget what else fits in that class. And the spec is for the piston as much as .054 out of the deck to get it.