Fuel vent line

You do need a vent. You will have to but a vent on the fill tube as a 1970 duster has. On a 71 the line going front attaches to the Breather on the motor. Those five lines going to that second tube can all be capped. One is your vent. The rest were a collision impact protection system that was discontinued in 71. I am leaving mine in place for originality. But the hoses will be blocked and I will only use the one going front for a vent plus a 79 vent.