GMC rear coil spring sus.

[Mike80D]

Every GMC pickup I have ran across has had leaf spring suspension, but I noticed on the 70 model I’m picking up that it has coils on the rear. My sales brochure lists coil as the standard, and leaf springs being an option so my truck can’t be some sort of anomaly I don’t reckon.
As far as the 551 med bronze/white paint, did they just forget to spray the inlay on the tailgate, or did that vary across plants? This is a St. Louis truck.