[jonzcustomshop]

GMC used these same letters on thier lcf/snub nose truck (I could not find a pic of a 66-square letters on a lcf..), on the hood, and on thier coe, bolted to a square panel in the grille shell.
the also used the square 66 letters in thier 7000-8000 series (this truck might have replaced the lcf/snub nose truck that was available 60-65)