I know you're trying to help, but, unfortunately, you're all out in left field. The female fitting on my gas tank has a Metric 2 x 1.5 thread or pitch. No One knows what I'm talking about trying to locate one or order one. Guess this forum fits right in.
Martin 1940D28
I see Martin, its the BUILT-IN fuel tank not the bracketed on tank. Silly us.
Incidentally, I'd just put petrol the tank - gas would leak out because its not a pressure tank and was only built for petrol!