That one fell out as I put the bike on eBay, a local engineering shop made one for $15 from the sample I gave him from the one on the other side of the bike.
Hi on my 91 the thread is 1/2" CEI ( 26TPI )I don't know if they changed thread size as the years went on ..
Tom regarding your build , I am about to do mine the same ,
not wishing to clog up the forum I have a load of questions if you get time would you get in touch [email protected]
That's the bottom stud for the rear subframe yeah?
If so, the parts book online section on this website lists the nut that screws onto it (for a 2001 500 bullet) as "NUT, 1/2" SHOULDERED, REAR MUDGUARD CARRIER, BOTTOM".