67-72 rear mount side fill fuel tank relocation question

[zacharywest34]

I'm installing a new rear mount side fill fuel tank in my 71 c20, and in the tank I got from brothers trucks there are a couple outlets on the tank I have no idea what goes to them or if I need them. I'm just running a mechanical fuel pump. In the picture here I know the green is the filler and vent but what are the other two?

[Mendo70C20]

vent tubes.

[Fbks_Cruiser]

I’m guessing this is a multi-application tank. I would think the other 2 ports are for a return line and vent. Since you have a C20, your truck probably originally had a vented cap, no EEC and no return line from the fuel pump.