Ken, just get a new nut & bolt - make that 2 sets for L & R & the 2 rollers - to make the shipping worthwhile, then shit-can the 40 year old stripped nut & bolt & be ready for the other side to break!
You may even want to pop for the replacement hinge brackets for L & R now, since the parts aren't that much, & they will go eventually (mine went about every 5-6 years & +/-50k miles when my DD).
No reason to go tightwad on this one, cause the old weakened parts will cause more stress on the hinges. My Great-grannie always said stuff like that was: "Pennywise & pound foolish!" & she was no big spender, being born in 1878 & through many Depressions!