71 Duster Fuel vent

FWIW, my '70 had a nipple near the top of the filler tube and a hardline that ran back down the outside of the tube and through a small hole in the filler tube to floor gasket. The end of the line actually just ended inside the frame rail. That's it for venting.

It would be easy enough to drill a hole near the top of the tube (stuff a rag inside to catch filings) and thread or JBWeld a small hose nipple in the hole. Connect a rubber vapor line and route it down through the trunk extension and out the hole in the drain plug.

I did something similar to this when I modified my fuel filler. In the pic you can barely see the brass fitting near the top of the filler tube (before lines were installed).

Or just use a working vented cap, as suggested :)

completedfillerimg.jpg