Shadango: Sounds like you need more "in person" opinions. Maybe put a shout-out to members in the Pittsburgh area?
It does sound like a cam, timing, convertor, gear ratio thing. A big cam could also be opening the power valve sporadically at idle, and the carb may need idle circuit changes, at the least.
That vacuum reading also could be a dead cylinder.
Ramcharger: You got it bass-ackwards! Turn the tire one revolution. Count the number of turns the driveshaft makes. 2 3/4 turns of the driveshaft equals 2.76. This works for a sure-grip or spool. Open diffs are "diff". :-) Maybe someone else knows.