Sounds like you have a bad vacuum leak. Are the gaskets under the carb & spacers good & cover all the openings? I don't know what the cam specks on that engine are but they probably are pretty strong. You will need to run more timing & hook the vacuum advance up to a full vacuum outlet. You may need to get an adjustable vacuum advance & set it for low vacuum. Check the float levels & set them a little high if necessary.
