GMC firewall markings, Pontiac plant

[davem815]

I searched the forum and could not find any information about GMC firewall markings. I’m still learning on 60-66 trucks.

I recently purchased a 1966 GMC ¾ ton that appears to be all original. I do not have the build sheet. The fire wall paint is original with the original markings. I can figure out what most of the markings mean, but I have a couple questions.

4669: this must be a build sequence number. It appears on the firewall, warrant book (hand written) and engine valve cover.
4669 on valve cover: looks like 7669, but is probably 4669 with the 4 angled and partially scratched off.

Tinted W/S: is pretty obvious, tinted windshield

EWQ: not 100% sure on letters for this one. No idea was it means.

Comfort: Comfort cab

555, written over top of comfort: no idea was this means. Interior paint/cloth code?

686 written near transmission tunnel: no idea was this means.

Writing behind and hidden by power brake booster and circle around mounting bolt: I assume means power brakes

Writing behind and hidden by heater: I assume means deluxe heater


Can anybody explain what some of these letters and numbers mean? Even if you can’t, maybe these pictures will help document originality for somebody else. I can post more picture or take specific picture upon rquest.

Any chance some of these number are paint codes? Very unlikely, because what would be the point of adding paint codes after the cab had already been painted? This is a yellow two-tone that doesn’t appear to me to be a standard color. The '66 GMC yellow appear much darker, I've seen it called yellow-orange. I don't have an actual paint sample, I'm comparing it to a downloaded '66 paint chart.