Rear shock upper mount

[3quartertime]

My 71 K20 has old worn out air-shocks on the back. I have some new Skyjackers to install but the air-shocks are mounted on a different (home-made looking) bracket. The original upper mount looks to be unused long enough that there is some pretty good rust and possible pitting going on.

My general plan is to wire brush it off to see how bad the pitting is. Anyone ever changed the upper rear mounting stud? Looks like I would need to grind the rivets off the fixture on the frame then drive out the mounting stud. My service manual and assembly manuals are kinda thin on this.

Thanks for any help!