First, I see your question has been answered. But let me just add this. Thank you for giving enough information for your question to be answered. Usually, there's no make model or anything else. We're just "supposed to know".
Also I agree with using it as a return line, but I would do it whether I went to EFI or not. It will help with keeping the fuel temperature down which in turn will help driveability with piss poor ethanol laced swill you have to run. It will make a difference. If you do it that way, make sire to run the return filter reference above by
@Car Nut. That filter has a return nipple with a drilled orifice to regulate the return flow so you don't lose fuel pressure.
I said nipple and orifice.
