i have a 84 f250 4x4. i wm replacing the rear tank with a 38gl. i got a new sending unit with it but i noticed the factory system has 2 lines on the tank. supply and return. new sending unit only has a supply line. how to u make it work? i would like to not have a return to the rear tank if possible... im thinking return only to front tank. this would alow me to switch from a 6 port tsv to a 3 port. one line to selector from each tank and then to the motor. and just run the return line into the front tank without having to go threw the tsf. any thoughts?