[SS Tim]

Having all the "stock trim" does not necessarily mean its original to that truck. The pictures previously posted clearly show much of the trim was off your truck when you bought it. Unless you can document that band as factory installed on that truck, I'd say it had been added somewhere along the line. This is based on the original stock trucks I know of and my research. From what I know of your truck as a Conventional Two-Tone (534) with upper (B85) and lower (BX2) bodyside moldings, it should have the upper and lower tailgate moldings with white painted letters.
Over the years a lot of trucks have been backfitted with upgrade parts and options.
Remember a tailgate is an easily swapped part.