Lets Play another round of "NAME THESE PARTS"

#2 has a self-locking nut (see impression on hex side) which would not be called for on a spare tire, my vote is to secure fuel tank strap (I just de-rusted and painted my strap bolt this week on a '65 A Body).

Its only 1/4 x 20 , I GOT ONE LAYING ON MY BENCH-----------