99xcss4
92g-94c frank'n (truburban) K-2500
hopefully they can give some good info over there definently never seen a truck with them just noticed you crossed the 20K reaction mark got some thing special made up for that but you are going to have to wait for your 5 year membership anniversary for it it will be going in the random picture threadThis is what I found on eBay. I remember the caps he had, having a GMC logo on the center though. Unfortunately most all of our family photos got lost in a fire a few years ago....
I looked in a 1978 Chevy truck accessories folder I have and they're not in it. I'm thinking these were mainly 73-75 or 76 at the latest. I'll ask on gmsb.com and see what those guys say....