I have a 55 Thunderbird that has the original carburetor and distributor. The car has been upgraded to 12 volts and I was told the engine was rebuilt at "some point".   I rebuilt the carb and fuel pump.  The vacuum advance can was also rebuilt. I plan to spend a couple of more weeks trying to optimize what I have before I make a decision.  My goal is to get the car to be more responsive, I am not looking to smoke the tires :-)
I am considering upgrading to a more modern carb and a distributor with mechanical advance.   Is it worth the expense to do these upgrades?

It seems better when I start in "Low" but still not 100%.   Are you saying Starting in Drive aggressively is the problem?