Nearly any engine from any timeframe can be tuned to run well for the particular application. Keep in mind that tuning does not simply involve one device, everything has to work in harmony. You have upgraded to an electronic ignition and had the carburetor rebuilt, but what about advance mechanism in the distributor? Is vacuum advance enabled in your particular set up? Wear and play in the valve train? You are making progress, each step along the way has yielded improvements. Not exactly certain the latest issue is? If you go to WOT everything is OK, but if you only go to half throttle there is a problem? or maybe it was half throttle to full that had hesitation? Also confusing is hesitation in the throttle travel? There should be no mechanical binding of the throttle shafts. When there is, its almost always been the butterflie are upside down.
Anytime an engine is called upon to increase output under load two main systems must work together, fuel enrichment and spark advance. Assume the carb is mostly OK, I would obtain a nice timing light and look at how well the timing advances. What timing at idle, what is the total, and when is it "all in"
Honestly, its running far better and not dying when you pour the coals to it, so personally I'd run it for awhile, enjoy the quirkiness, then create a list of things you would like to change. Plenty of time over the cold winter to tinker.
