95% of all carburetion problems are ignition.
But...
the Opinionated Pipefitter posted:... but back to the black plugs. I'd be willing to bet that even a properly set up and operating ignition won't fix the black plugs. Hotter plugs might help, but I'd be willing to bet money that the problem isn't ignition at all. I'd bet you have dual Kadrons, don't you?
Kadrons always run rich. You can work on leaning them out, but they're pretty bad on the idle circuits and the needle and seat are really terrible. If you are generally satisfied with how the car runs (and with getting less than 20 mpg with a sub-100 hp engine), then change the cap/rotor/wires and the spark-plugs with something at least one step hotter.
Good luck.