The symptoms you describe sounds more like a timing issue than carburetor. You mention resetting the timing, what did you set it at? You may need to advance it over the stock setting, as the ethanol fuel we have these days needs more advance than the fuel that the older vehicles were designed to run on originally. You should also check both the vacuum and mechanical advance mechanisms to be certain they are working properly.
On the carb side of things, check for vacuum leaks. You may also want to go back to the larger 325 intake and carb, though I don't believe that's what is causing the problem.
