Front Shock Lower Mount

I would just re-thread it to the next smaller SAE, all the nut does is retail  the shock from moving in the stud. Rethreading,  you are retaining the stud.

Thanks, Alan. I thought about gluing the nut on.

I also thought maybe it is a stud I could unscrew and replace.

Yes, it is a removable stud, but I can’t remember if it is threaded in or not.

What I do remember is that there is a roll pin (sometimes called a “torsion pin”) inserted through the shock mount and through the stud about an inch inboard from the mount/stud intersection towards the ball joint on the trailing arm.  The pin is pressed in vertically so if you look on top of the casting in that position you should see it.  Bang it through with a suitable punch and hammer and then you should be able to replace the stud.

When the new stud is installed, you’ll have to re-drill the hole through the (new) stud the same size as the hole in the mount and insert a new roll pin.

Or, you can just do it the easy way as Alan suggested.  

Worst case scenario, replace the lower trailing arm on that side. You've already got it half-way off due to replacing the ball-joint boots. One big nut/set screw and swap it out.

Alan is spot on. Just thread it with the next size down and you should be fine.