72 Demon fuel fill vent tube ideas?

If the tank is for the correct year, the vent is in the tank, NOT the sender

You tank should match the diagram I posted above.

Otherwise, I'd say yeh, weld a flush fitting in. That should be easy, say, if you can silver braze. "Mike" the fender hole so you know what you have to work with. You might be able to notch the fender hole a bit if the gasket will cover it.

Yes, The new tank did have a vent tube high up in the front which I plugged shut as I did not want to run a line and do not have a charcoal filter. I was intending on doing the older style vent in the fill tube, but as I said, the fill tube goes into the quarter panel from the outside with no room for anything but the tube to pass through. So I am trying to figure out how I can install the threads without having them protrude so I can screw in a fitting after the tube is installed. How do these bungs work in a curved wall of a tube/exhaust ect without sticking out?