If there is enough material in the welded on hex nut, I would drill and tap for 1/8" pipe, it will save money and time. All it has to do is hold a fuel line. Add some of the strongest Lock-tite when assembling and you should be good to go for years.
There are carburetor repair kits for the fuel inlet that are stripped out, you may look into one of those. 1/4" pipe is next size up isn't it? You could also solder in the new fitting if the threads don't look deep enough or hold as well as you like.
Joe
