For anyone following along:
I pulled the bed, which took maybe an hour. This was aided by the fact that it was exceedingly easy to remove the 4 clamps because they were barely right.
I first noticed that they cut off one of the old bed bolts and left half of it in the nut clipped to the frame. Not surprising.
I also noticed that they clipped the old brake light/signal wires, left the wires unterminated and then left the harness plugged in even though it went nowhere else. Also, not surprising.
And finally I noticed that they didn't even use the right size vent hose for the filler neck, which I did think to grab a picture of, even though I was still not surprised.
Now that we're free of all of their handy work, here's what we have going on....
I cut 4 crossmembers out of 3/16 wall 2x2 tube. The front and rear are on spacers made from some 3/4" thick bar stock. They're all on sitting on 3/4" thick, 2" diameter polyurethane donuts sold as CJ body mounts, and bolted into the original bed mounting holes in the frame using grade 8 bolts and lock nuts.
Then, we have some 1/4" thick 4" angle bolted to the crossmembers (again grade 8 with lock nuts) to create a channel that the new bed will sit in. The damaged long sills will rest on the horizontal leg of the angle and bolt into the vertical leg.
In total, this should put me at about 3" higher than I was, with a lot of extra strength (plus, it won't even be twisted and wonky).
Also, I have some heavier duty springs installed, and when I was bringing home the steel for this, it rode SO much better than with the flatbed alone. The little bit of extra weight will be welcome even though it's probably overkill.