My '80 Z has 3 fuel lines - supply, return, vapor. I am looking at different fuel pump options to get more flow at higher RPM's (mild 383 spinning up to maybe 6500 RPM's with a Q-Jet).

I was going to get a Carter Musclecar Pump (Summit #: CRT-M6624 for $21.69) and be done with it, but then I saw the return line.

Can someone please explain how a return line can be utilized with a mechanical fuel pump? My stock pump had two inlets, and one outlet. I have not come across any aftermarkets with the same setup.

Should I just cap off the return line? Is that safe? Or is there another way to do this?

If a pump is not setup for a return then it's designed to operate as a dead head style pump. The return is simply capped off and not used. Very common.

Since I have the tank out & I'm replacing the hard lines, is there a good reason why I shouldn't just swith to a 2-line setup with a single-line sender unit?

Since I have the tank out & I'm replacing the hard lines, is there a good reason why I shouldn't just swith to a 2-line setup with a single-line sender unit?

if i remember correctly,, doing that will require a vented gas cap. otherwise,, fine and dandy. maybe someone else had more input.