Looks like a beauty, nice color. Do you know if the round headlights and amber corner lenses were swapped in at some point? 1980 6 cylinder models (both diesel and the gas V6) would have come from the factory with quad rectangular headlamps and clear corner lenses, although the 4-cylinder gas engine cars did have this round/amber setup in 1980, final year before the rectangular/clear setup became standard across the line.
Maybe someone liked this look better and changed it over. Anyway a diesel with round headlamps is a rare item, and it looks good on your car.
Good luck with the sale, if it doesn't find a good home here, you might consider submitting to Bring A Trailer -- well preserved original survivor vehicles like yours seem to have a good audience and market there.