Adam's Scamp

I bet that is some kind of stand pipe like plumbers use, one that lets the fuel vapors expand some when the tank heats up. That way the fuel cap can be a non-vented one and the charcoal vapor canister can do it's job of recovering vented fuel, ie, california stuff. I just checked in all my pictures of my 68 barracuda and found I don't have a truck picture yet, so I don't know if my cali car has one or not. I don't remember seeing one.