1967 c10 gas tank

[dave`12]

Hello. I have a 67 c10 with the tank behind the seat. It is probably not the original tank. I smell fumes in the cab, so I'm trying to fix it. Got some questions about all the lines. I have the ecc tank because it has the hose going to the inlet.

There are two lines off the fuel tank sending unit. One obviously goes to the engine. The other is just pinched, no cap or anything. What should I do with this other line? Does it need to breathe, or can I cap it? Behind the passenger is another line coming out, this appears to be a vent, just a hose a foot or so long. So, does anyone know what I can do to get the fumes out? I don't see a way to allow the hose behind the passenger to get out of the cab (no holes in the floor).

Any help appreciated.