Ok, I went and looked at a 1986 D100 today. Didn't have enough time to drive it, so I'll probably go back again. Overall impression: not bad, definately a work truck. Driver's side floorpan had been replaced / metal riveted over it. Ok, didn't seem like the cab was sagging, like on Chevy's, so, won't worry much. Underneath, truck was oiled every couple years with chainsaw oil (!), so it actually was low rust--apparently the door seals gave out, and the carpet is what took out the floor. [The wing vents were sealed shut, and I think the door seal was missing around the door too--open the door, and all I saw was a metal lip, no seal, on the floor area.]

However, the biggest issue was above the windshield: all the metal underneath the drip rail, from the windshield to just above the drip rail on the roof, was replaced with RTV. Pretty sure a windshield replacement would be, err, fun... Actually, I think only the metal on one side of the cab, so it wasn't the entire strip above the windshield; but still... 2-3 inches tall, by say 6 to 8 inches long?

Just to verify, that drip rail is welded onto the cab, for its entire length? I presume there is no commercially available patch panel for this area, so any needed repair would be homemade. Also, the door seal, that is affixed to the cab and not to the door, right?

I guess I wouldn't be interested if the rest of it seemed to be such low rust and decent shape. I'm hoping to go back in a few days when the fog of this cold dissapates--I was thrown the whole time by the missing leanburn computer--only to realize after leaving that it's on the fender for this year not the aircleaner.

Cam across a link that said that the drip rail is caulked (at the factory), and that the caulk can dry out over time, giving the rust that I saw. So, not unheard of / not uncommon. When I go back I'll have to see just how much was removed.