[1969 GMC]

Some things I know I can add:
-1970 had optional disc brakes (for 2wd only I think, should be listed on option sticker)
-1971 had a "Disc Brakes" sticker on the tailgate
-1971 Cheyenne Super Glove Box trim badge has no fancy scripty shapes; 1972 Cheyenne Super does have them.

For GMCs:
-67 said GMC in the middle of the grille, had sloped hood w/ no GMC letters, no upper trim or "eyebrows"
-68 had sloped hood with GMC letters on front, and no upper trim or "eyebrows"
-69/70 had chrome grilles, top trim piece, and eyebrows; sloped hood no longer used; black paint around outside of headlight bezels
-71/72 had black stripe that went around the perimeter of the grille and down thru the center

Longhorn available 68-72, 2wd only, C/20 or C/30 only

Blazer 69-72, no 2wd '69 Blazers, Jimmy introduced in '70. All Blazers wear K/5 badges, even if 2wd.

phew