1 bbl carb

I have a 71 Dart Swinger with a 198. Starting running poorly a few weeks ago after a day of a lot of driving. Much has been done since including a new gas tank and pickup/sender (old tank was really bad) plugs, wires, cap and rotor, fuel pump, carb rebuild (but original float), ballast resistor. Still having problems which I believe is still the carb. Odd thing is it will occassionally run ok for a few seconds or even a short drive but will return to hesitating, stalling. I have the Holley 1920 and have read here that a lot of you prefer the Carter bbs. But I really cannot find either available new or rebuilt so figured putting it out to you guys was the next step. My end game for this car is to put a 318 4 bbl in but for now I just want to get back on the road. Any suggestions are appreciated. I'm in the metro Detroit area