the front mount is a solid bung
the rear peg bolt is a hollow section with a nut tack welded inside of it
(i say "tack welded" very loosely)
when i went to re-install my nerfs/pegs the other day, those 4 very tiny "tack" welds broke and the nut was in there floating around.
i cut the solid front mount from my spare frame, drilled the rear hollow section out to fit the new solid piece and welded it in there.
so if yours is the rear one, be very careful drilling and re-tapping it, so that nut doesnt break loose.
the bolts are indeed 10 x 1.25, and usually the next bigger size american is closer than the next size metric,
so check into the drill/tap bronco mentions above