Years ago (many years ago) I figured out that a 1/2" distributor wrench fits that doggoned nut under the float bowl perfectly. You know, that one that's so tight you can't get anything reasonable in there? Well this wrench works flawlessly. If I find the pic I had way back when I'll post it.
Yup, most mechanics have a collection of wrenches that have been heated and bent, or ground on or just made out right to solve problems like that. I do, you cant do without them when you need them. Of course it may be 5 yrs before I need them again. I still have some modified wrenches from the 50s and i save them ''just in case''.