AutoLite Platinum AP145 cross references to AC MR44T and R42T, the R42T is the colder plug, R44T would be standard heat range.
Also crosses to NGK 4581 and YR5VX.

Factory original plug was R45T or R45TS, (S = extended tip).
The R44T is just one range colder, which might be helpful with today's fuel in an older engine like yours.

The AP145 was the correct interchange for the original plugs if converting to Platinum style using AutoLite's.


Spark plug choice is most likely not your issue with "doggy out of the hole"....that is more likely either carb jetting/carb needle/step-up piston springs or low ignition timing.
An out of the box Edelbrock 1406 is not going to be tuned correct for your engine, just tuned good enough to get you running after a carb swap. It will need a full retune to work best, using the tuning kit for that style carb.

 

Could be sub 3.0 rear end

 

Doggy out of the hole is also a lack of rear gearing or a miss match of cam to torque converter with an automatic

Probably time to upgrade the ignition as points and condenser are obsolete by 50 years. Not that they can’t be made to work decently but these days they aren’t well made for either part and points put a physical side load on the distributor shaft which results in bearing wear that allows the shaft to wobble making getting consistent dwell difficult to get from cylinder to cylinder. One of my first changes beyond testing for rear axle gear ratio is putting an HEI Ignition on the engine.

Bogie

 

I am not sure if I want to upgrade to not using points and condensor, but I realize what you suggest and mean and pertronix makes it easy, if that is all it takes.