Suburban tailgate strap bolt issue

[91_Suburban]

Trying to replace the tailgate straps on my 91 Suburban, because whatever nut is presumably welded on behind the body panel has come loose, and the bolt just spins.

So, I'm looking for advice from someone who's hopefully been here before me, in descending order of importance...

1) Is there a bolt I can get as a replacement which includes the thicker unthreaded portion, or will I be looking for some bushing stock and a big washer to rig something up?
2) Any good way to remove the weld on nut behind there instead of letting it fall into the body to remain for eternity after I cut this bolt that doesn't involve cutting the truck open? (At that point I'll just leave it). Going in through the connector slot above it won't work afaict, there's another panel in there concealing the nut.
3) I'm thinking replace the nut with an appropriately sized rivnut. Any better alternatives anyone has tried? I'd probably start a fire on the rustproofing if I welded it. Rivnut seems like I'd avoid damaging the paint in a large area.

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[Big Chip]

Have you taken the tail light or the side panel out to see if there's access?

 

[91_Suburban]

Have you taken the tail light or the side panel out to see if there's access?

Yes, back when the nut first broke off in there. Going in and turning to the left, don't have a good picture of it, but there's metal all along, no crossing back over through there. There's at least 2 more layers of sheet metal between the two cavities. The closest I can get is by going in by the connector up above the tailgate strap bolt, but there's another sheet metal layer blocking me off there as well.

I suppose the most clever option is to drill the spot welds surrounding the strap bolt and attempting to re-weld them.

 

[Big Chip]

They don't make that convenient, do they? I don't have a suburban and couldn't picture how it was all set up in that area.

What does it look like from inside the truck looking back at the area where the bolt goes through that pillar?