I'm not sure that that truck has original, as in never had a re-spray of any kind, paint.
There are tell tale signs that say otherwise. Overspray on the radiator support decals, missing tailgate letter/decals etc...
My 1981 has a lot of original paint on it, but I wouldn't say the whole truck had original paint. Original color maybe. I've replaced the tailgate twice for example. The engine has been painted at least three times.
Original paint can mean different things to different people I suppose.
Truck: 1981 F-150 Explorer / Engine: 300-6 California MCU Feedback System / Trans: T-18 - 4 speed / 2.75 Ford Rear Axle Open Diff.