That is one of the interesting things about these trucks, (& other models with many year runs with some variations) people come up with whatever they find, have, can get cheap, want it to look like, be, ect. ect. Unless you start matching option codes...much of this goes unnoticed to the average person. 2wd become 4x4's, '70's have 80's fronts, 6cyl end up with V8's, Diesels get gas engines.
If only the horn cap, dash emblem & the tailgate have been changed...your truck in pretty much original when "grading on a curve"

Enjoy! Lorne