Got a little more practice welding spare parts together, tuning in the settings on my welder & figuring out what works on various thickness metals, so why not take off the hitch, & rear bumper, and tailgate so I could dig into the rear crossmember... which looked exactly as I expected, rotted out! The crossmember was just gone, but the floor wasn't bad, actually in much better shape than I expected.
The first part was the worst, taking off the damn bolts on trailer hitch! Each of the 6 bolts fought me hard. I could only get 1/4 rotation with a 4' pipe on a breaker bar, right to the very last thread on every single bolt. I didn't want to use heat right next to the gas tank & my impact wouldn't budge any of them. Then taking off the bumper, & tailgate weren't too bad after that.
Then I drilled out the spot welds & carefully separated the floor from the crossmember. Time consuming, but not bad, removing the crossmember in pieces with my cutting wheel along the way, which made it easier to work in that tight area. The body mounts didn't need to be unscrewed cuz they had rotted thru the frame & lifted right out, which is typical in so many Bronco's, but it was easily repaired with 3/16" plate steel. Its nice & strong now, and I can weld in the crossmember next, then tie in everything else back there. I thought this job would be scary, but i watched enough repair videos to feel confident to tackle this & honestly, it wasn't bad at all.
It took about 2 hours to get the crossmember out in pieces, & frame cleaned up, and then another hour to fit & weld the 3/16" plate in to cover the holes in the frame. It wasn't bad to do at all, and quite satisfying to tackle this elephant in the room I knew was lurking back there.