Dave, Dave, Dave...
You need to sync the carbs, then if you still have a problem, pursue it further.

By synchronizing, not only are making the carbs have their throttle plates open the same amount at idle, but you are making the throttle plates open at the same time. You are also setting the idle air screws at exactly the same position (if equiped) and the mixture screws at exactly the same position. Both carbs need to be identical in operation and setting to one another.

Once you accomplish that, then you make 100% certain that the linkage which connects both carbs together, does not hold one, or both carbs partially open once it's reinstalled.

This is a big deal, and the car will never run properly until the carbs are synch'd correctly.......no matter what other parts you throw at it.

There are half a dozen things that will cause your lean stumble on acceleration. Wiggling your foot simply proves that the problem is due to a lean mixture. That momentary lean condition can be caused by......wait for it......half a dozen things.

Re: the carbon core plug wires. Carbon core wires are typically very high resistance. Carbon core coil wires typically fail internally and can cause your problem. In a points ignition car, you want it the way the factory had it. Solid core wires with resistor ends, and non-resistor plugs. Unfortunately, you can no longer buy non-resistor plugs in the US, unless you find someone with some new old stock.

Use caution when buying non OE parts. I can't tell you how many times I've fixed drivability problems (like yours, and others) by simply removing all the wiz-bang, aftermarket, look-a-like, Bosch wanna-be, cr@p that people buy and put on their cars.

One last thing. Are you sure 6BTDC is correct for your idle timing? My '66 Coupe is set to 30BTDC at 3,000rpm+ and that winds up being 2-1/2ATDC at idle with the vacuum retard. I'm not saying your 6cyl is set up the same way, but you might check the book spec.

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