Broken rear shock mounting stud

I'm putting a 68 Dart GTS back on the road after sitting on jack stands for 21 years so there's a little rust on the underside. While replacing the rear shocks the drivers side was difficult but I got the nut off the lower stud. The passenger side was problem though. After penetrating fluid, heat, and working it real slow the stud still twisted off.

I can't tell if that stud is welded in or whether it screws in.

I've looked online for diagrams and find nothing. I've also searched all the restoration sites and can't find the lower leaf spring mount with the stud in it.

So, I need some help here in which direction to go and what I'm ultimately going to replace.

Thanks...