FYI Department:
More info on the welded nut&washer I found under the couch: Under the front seat, I found two more nuts and a large 3/4x6" bolt with a two inch thick rubber mount around it that the washer/nut is meant to keep on.
One nut, okay— but finding THREE MORE and the bolt was too vexing to ignore, so I took them down to the Ford Truck dealer and they said it was a mount that's meant to keep the cab affixed to the chassis. I have to bring the Plus back in this week for an inspection.
I also asked about extensions for the tire valve stems and the mechanic who fixed the dash asked if I'd ever heard of, "Cat's Eyes for truck wheels?" I said no of course and he showed me some he had installed on another RV.
They are snake-like metal hoses that connect to the double rear wheels with a gage (that looks like a cat's eye when the pressure is correct) letting you know if you need more air.
They also equalize the pressure in both tires— which is somewhat hazardous when they aren't equal.
And finally, they ordered me the proper Econoline front mats--which they said, I'd never be able to find in an auto parts store.