Well I know nothings been touched for decades as the guy I got it from dugvit out of blackberries where it was completely submerged for decades, nobody even knew it was there. Question is if the cab swap was in the fifties or in the eighties or somewhere in between, just not after that. Seeing the lincoln county on the tires is the only reason on the whole truck that I suspected it was a government truck, knew nothing about the truck when I got it except that it was a napco. Napco parts look like they've been on the frame since new. Cab, front clip, and possibly engine look like they were replaced once upon a time, as the whole front bumper was ripped off and the front engine support is just a massive 1/2 inch plate that runs from one framerail to the other. Maybe a tree fell on it parallel to the truck, but they decided to reuse the truck because it had the Napco drivetrain. My question now is how to determine if the engine is numbers matching, so I can know whether or not engine is original to frame. I think napvo components and transmission are original to frame, but who knows.