gas tank vent?

I know this is an old post however I have a similar problem my new sending unit has two lines one for fuel coming out and the second one for venting I’m doing a 1969 Dodge dart convertible. On the feeder of the fuel tank there is a second line it looks like 5/16 tube is that the vent line? Or do I bring a second line all the way to the engine Compartment just for the vent tube