Improving acceleration using 2bbl Carburetor?

Have you checked for any vacuum leaks ? A vacuum leak would cause your car to run poopy.
It certainly can be fuel related to. Get a clean gas can, and run a line to the fuel pump and see how it runs.
Take the carb off and clean it. Take out the jets, a/f , and blow compressed air through all the the passages. I'm assuming your mechanic knows how to adjust the a/f and idle correctly?
How's your timing ?
A well running 2bbl /6 runs well, with much more get up and go over a 1bbl.