We swapped a chevy 305 engine/350 trans out of a 79 camaro, into a 54 chevy pick up. It has a 2 barreel carb with a fuel intake in the front and an outlet in the rear. If I plug the rear outlet, the carb overfills. If I run it directly to the fuel tank the truck runs terrible. When I squeeze the line it runs good.

My question is, how do I restrict it, by how much or can I just loop it back to the inlet side? thanks for your ideas.