Quote:

I thought it was done to keep from laying down on the big end when the revs come up and the increasing vac. lets the pv close?


If the carb is truly too small and you're seeing vac on the big end could be an issue. Vac gauge in the cockpit will solve that mystery.
When I tried plugging and square the car just was ill behaved on and off the trailer, around the pits, etc, as one might expect, depending on the combo.

70 Sport Fury
68 Charger
69 Coronet
72 RR