Hey man, I'm semi-retired,covid is a *****, no kids are home for Christmas, I got the day off; and I'd love to get to the bottom of this,
So; I'm here for you.
Besides; I'm tired of playing Spider Solitaire,lol.
I am active duty military, but went to college and was ase certified. Over the last 20 years i have built and restored many cars, but no performance motors other than a few 350's and 400's. I never had an issue like this.
As far as the cr discrepancy heads are 63cc vs 65cc.
Using the Wallace which takes into consideration the head gasket diameter it is 9.8-1.
The only reason for the 7177 cam was that edelbrock recommended it for a match with the heads and intake, but doesn't seem like a good match after all. I found several posts last night from others with similar vacuum issues that had a problem with lifters(coming apart, becoming flat, and other issues). I had one that would never prime after setting the lifter preload and was sent a replacement.
Speaking with two reputable machine shops here that everyone uses to build the race and demolition derby motors they made similar comments to you.
Dynamic compression with aluminum heads 8.2-8.4 and 8.0 for cast iron heads.
My compression test was done cold wide open throttle with plugs removed. Cranked over 4 times watching needle jump and recording the number.
Elevation for my area is 6854ft.