GMCJR, Thanks for the info and the MUCH needed photos.
I've discovered that the fitting on the Solex is infact metric, BUT that the 5/16th fitting is so close that it will work as long as it goes in with a little love and care.
In the morning i'm out to do more investigation. Idealy I'd love to find a ??Metric to 1/4 adapter but out here in the desert hopes for that aren't high. I'm also wondering about replacing the banjo with one that's standard thread. I need a rigid solution regardless as i'm going to hang a Carter sediment filter right off the carb, so a barbed fitting with some hose just won't cut it.
-John