Would "GAFB" be Glasgow Air Force Base, then? Would make sense, being local to Montana and having SAC (B-52 and KC-135) assets there about the right time frame for a truck of that vintage.
There are some Zoomies over on Steelsoldiers.com who can probably give you some insight on that truck (if the Stovebolt Zoomies don't mind some back up).
Fascinating truck!
Even if it is Air Force ...
