I have an 84 Z28, swapped in 355 w/ 5 speed. I have an edelbrock 1406 carb w/ edelbrock mechanical fuel pump. This pump has no provision for vapor return. My question is if I go with an electric external pump, would I be able to run the return off the regulator to the old vapor return line? really dont wanna drop the tank if I dont have to....

 

Welcome aboard thirdgen.org.

Let's be clear on terms here. There is no "vapor return line". There is a fuel supply line, a fuel return line, and a vapor recovery line. The fuel return line is 5/16", which is smaller than the fuel supply line, 3/8". The vapor recovery line goes to the charcoal canister.

The stock 5/16" fuel return line is fine for any electric fuel pump that you should consider using on your car.

The Carter M6626 is a high-flow replacement pump for the factory mechanical with return. You might want to consider that as an inexpensive alternative to an electric pump and return-style regulator.