Waste of time, all that's needed there is to plug the vacuum sources you unplugged at that time and the cars run forever with no smog, I did an MII '74 model same engine and it ran forever, took a 6 inch hailstone storm to take it off the streets in '95. No magic there, I'd bet a million on carb internal error or fuel supply issues there. Why all the vac leak testing showed nothing but still a hundred other places you can error there. Your race guys should well know that, I built plenty of race carbs and motors myself. That little carb there often stymies race carb guys as Holley carbs are so simple that 1st graders understand them, not so that carb.
And, IF car was running fine before then why did we mess with the carb to begin with? FYI, I have heard that 'it ran fine before I...' line so many times it goes in one ear and out the other on a 6 lane freeway, often it turns out to be totally false. NO INSULT INTENDED AT ALL BUT when one says that they lock themselves into not weeding out all other choices by the people helping and often results in the poster NEVER getting the problem fixed. I've seen it a 100+ times and why most GOOD repair guys often ignore everything a person says about a car and previous conditions so he can start with a clean slate to easily figure out the problem. Sorry, but often the ONLY way they get fixed.
And why compression test keeps getting mentioned..... ...........the car is a '74 with no induction hardened valve seats, if the 14 year timeline is right then it could have been driven for years after all fuel went from low lead to true 100% unleaded around '93 or so and the valve seats could be dead as a doornail to have the car not run right at all. The same MII I reference above began to have severe valve problems every 10,000 miles after the fuel changed. Another valve job and back to running fine until they die again. Idle going to crap is what shows up first to most novices, power will drop off before that but low enough amount that most will not notice and claim 'it runs fine', sound familiar?