[jocko]

My 2 cents - the 67 data book states that all trucks had off-white tailgate lettering, except for white, off-white, and silver trucks, which had black lettering. So trim level should have no bearing on tailgate lettering paint presence.

As for the question of whether or not the tailgates "should" have painted letters, I'd say that should be a yes.
As for the question of whether all tailgates actually had their tailgate letters painted by the factory, who knows - lots of examples to the contrary above.

While I think we all have a good eye to be able to tell if paint looks original, sometimes it's easy to forget that these trucks are now 50-55 years old, and a 40-45 year old repaint can look pretty darn original, faded, and rusty now. Great data points above to scratch one's chin on though.