Replacing fuel system

[Hankrebel]

Im replacing the fuel tank, lines and pump in my 71 Swinger.
I already have the 4 vent tank, pump and lines.
It also has a vent running to the front for the 3 nipple breather cap.
Do I really need this vent line if I already have the 4 vents going to the trunk tube?

 

[Garrett Ellison]

The line to the 3 tube breather allows the PCV to pull fuel vapor from the trunk tube through to the intake manifold after it passes through the right side valve cover. So in a word, yes. Fixing 1970s Evaporation Control Systems