Need help figuring out my fuel lines on my 1972 suburban

[Mikmark]

My 72 has two lines that run to the fuel tank. One brings fuel from the tank and the other returns fuel back to the tank. I think this was to help keep the fuel cooler and avoid vapor lock. The original fuel level guage that fits in the gas tank had a port for the return line. The replacement ones that I have looked at do not have this extra port. I just ran the return line to one of the vent ports. Works OK so far.