Gas tank woes. Options

[Olympic 914]

its been MANY years since there was fuel in my gas tank and I wanted to get the tank cleaned out, change the sock etc. before I tried starting this thing.

Well first off the tank looked pretty good inside, with just one spot with rust. so I put in some Evapo-rust and sloshed it around for a couple days, then took a long screwdriver and scraped at the rust, well this uncovered a couple pinholes. there is a tank repair shop near me and they cleaned up the area and welded a small patch on the area and then pressure tested it, all good.

Then I painted it up and decided to change the fuel sock. well when unscrewing the aluminum nut holding the fuel sock in some of the threads remained on the fitting.

so now I need a new nut and also

Does anyone know the size/thread of that fitting? I tried cleaning it up but a fine triangle file just isn't going to cut it without screwing up the threads. So I think I may have to get a die to refresh the threads. and clean out the aluminum..

I don't have any dies that big