Vapor port on fuel tank

My '73 Duster fuel tank has a hose fitting on the top, presumably for the vapor capture setup that was originally on the car.

That fitting is connected to a vapor separator inside the tank? As such, the fitting could NOT be used as a return line?

Not for EFI, but for a fuel return to help lower fuel temps...something to plumb my bypass Holley -841 regulator to.

Thanks.