I would just use a fuel line plug and plug the line you don't need and then put a DuBro Kwik fill on a 90 degree bent piece of sturdy aluminum stock on the firewall just in far enough so the cowling clears it. Drill the aluminum stock with a 3/8" bit and the quick fill will slide through and then add the nut for a secure fit. Then drill a hole in the cowling where the fuel fill is and you can fuel the plane without taking off the cowling. A fuel dot requires removing the fuel line every time you need to remove the cowling. A nice feature about the Kwik Fill is it shuts the fuel off to the carburetor when fueling to avoid flooding. If the fuel come out the muffler it is full. I usually make my cut out on the cowling for the muffler large enough so I can get to the fuel line and remove it when fueling. That way you don't fill up the muffler. When the fuel comes out the line it's full. This is just my method and it works great.

Gibbs