[GMCNUT]

Jeremy, the 1960-61 and 62 grille supports in both GMC and Chevy used a slightly altered lower lip design vs the 63-66 style because of the different frame, and since 60-61 had 4 headlights vs the deeper single bulb in 62, the stamping behind the headlights on each side is shaped to fit the depth of the headlight bulbs. The 63 grille headlight bracket re-design eliminated the need for a 4th bolt to secure the grille to the panel so 63-66 panels will only have 3 pre-drilled holes where your GMC grill requires 4 bolts per side. I am not sure exactly what the difference is between a 63 and 64-66 panels but I assume its is something unimportant really. They should actually be the same. So, for you to get a panel w/ 4 holes on each side you would have to get a 63-66 panel and drill the extra two holes, or just leave the two extra bolts out of the grill (3 is sufficient to secure it well anyway). Hope this helps - also I have a couple of perfectly straight rust and bondo free 63-66 panels for sale or I know where a 66 GMC is that I can go get you that one and it would be exactly the right one. PM me if I can help