After I got the floor pans in, I took on the left rear where it had been backed into something wrinkling the engine cover, the rear valance panel between the bumperettes and shoving the left rear bumper guard into the rear cross member. The rear tip of the quarter panel above the taillight was also pushed down.
I made a couple of abortive attempts to pull the cross member back out with weld-on studs, but that didn’t work at all. So, out came the damaged part of the rear cross member, and the fab process started.
Built a wooden form,
shaped a panel to fit,
And welded it in. That all looked pretty good, though it turned out ultimately it wasn’t good enough.