Had a bit of time in the shop last night - Figured it was time to rip the Bandaid off and start figuring out what to do about the license plate / roll pan section. This piece is trashed - there are no donors available, nor accurate panels available from any of the guys in the Econoline community.
Little difficult to see with the tailgate affixed in this photo, but you can see that it is a bit worse for wear, to say the least.
I started by cutting along the spot welds holding the top section flange to the bed floor. Worked all the way to the passenger side to the edge of the flange. From there, there are some small stitches that needed to be cut open. Below the red arrow on the right side, is a stitch that holds the corner section of the bed to the flange of the roll pan. It had rotted out above that stitch, so the cut was made above that.
Looking from the rear, there are a couple more small stitches to cut.
Alternative view
Those stitches were cut, along with a few additional plunges to release the panel from the bed and body.

Flip it over and start removing the guts and everything that isn’t the panel we want.
Freeing up these spot welded flanges from the roll pan backer, bed, and other connection points.
I’ll finish getting all of the remaining flanges off this panel - and then start taking measurements to make a new one.
Hopefully be able to make my final panel weld this weekend as well, but when I hear overtime at the day job i come running, so we’ll see.