Unless someone has completely changed the plumbing for your fuel tank, that IS th fuel vent. Some guys plumb them to the air filter outer bonnet.
There are some threads on this. Some years-----72, Ma used external vapor separators. I believe some, up around 73? 74? later? used a vapor separator built into the tank. That line originally tied in with the carbon canister.
As I said, it IS the tank vent
Some of these threads are not entirely correct because of the year, but this is the idea...........
