Hey Ross so I have 2 quick fuel 750s from Barry. Blair went through them but I think it ran good on dyno but not in my car. Originally carbs came with 72/81 so that’s what I have in the front carb except he had a 5.5 PV and I put a 6.5 in which it came with. I haven’t taken the rear carb apart because my carbs are progressive so I was just trying to get it to drive around fine because when I stomp on it it runs great except for a little bog off the line which I really can’t duplicate on the street because it just spins the tires but at the reunion my 60 ft times were way off. I do know that the rear carb has the rear PV bolcked with the jets upped to make up for that. I guess it could be wires I was swapping them around maybe it was making connections and loosing it. I also thought about the cap and rotor so I changed them last week. I even bought one of those adjustable rotors which I haven’t used.
To me it seems like a miss that comes and goes, with no other indicators, and valves adjusted correctly, etc, two sets of plugs, almost has to be a wire. The cap end can be tricky sometimes and I have seen them break where you fold them over. Not often but can happen
As far as the carbs, the 6.5 would bring fuel in earlier, but I'd probably see if you can find something with the plug first, then tune later. As far as tuning the carbs, I generally like to start with basics, get them to a known good setup, usually as delivered, make sure accelerator pumps are working immediately and adjusted correctly, make sure both primary and secondary idle are correct and float levels are correct, and then start making one change at a time.
My gut says the dyno liked a little less fuel, and one jet size isn't going to fight you either way, my guess is intermittent spark on one or many. There is an old saying that most carb problems are ignition problems, can't say it IS the case, but seems like it here