[mr0077]

David, my first impulse is that your current problem is due to having the carb too lean now, after the jet change...did you change all four jets? Has the car always had the rich odor and sooty plugs? If it ran okay then went rich, maybe your jets were close to right but you blew a power valve (causing it to go rich on you), and giving you the indication that the jets were too rich? And, the late advance curve and reversed polarity on the MSD certainly didn't help with the drivability problems.
One (not very tasty) way to check the power valve on the cheap is to pull it out and suck on it (clean it off first!), or, get a tester (where?) or just change it. If it has a vacuum leak it's no bueno if the needle moves off the seat with no apparent leak, it should be working "okay"...
Too bad the choke horn is milled off...if you could find the Holley part number you could look through their online tech info and see what jets and power valve it should have.
What vacuum are you pulling at idle? Make sure the power valve is rated a couple of inches lower (smaller number) than your idle vacuum reading.
If the power valve is good, I would think it is accelerator pump problems, or a combination of lean jeting and pump shot(s) too small...
If you have an MSD distributor, I'd recommend recurving with an MSD blue or silver stop bushing and the light blue and silver springs (MSD curve "E"), and set total advance about where you have it at 35...in any case, getting the advance all in by 3000 RPM should improve the drivability.
BTW, tell us a bit about the reversed polarity issue...what are the symptoms of reversed polarity, how do we check that? I'm like Snakecharmer, hadn't heard about that.