After reading Your post this morning You got me curious, you are correct about what GSC means but as for rest I can’t find any thing. All I know is they are from Budd pass. cars. I found them in the Walters catalog. Now I too want to know what the rest means.
There was an article in the February, 2005, MR by Kevin Holland called “Modeler’s Guide to Lightweight Passenger Trucks”. In the article was a section called “Cracking the Pullman code”. According to the article, the 41 meant that there were four wheels in the truck, and that there was 1 truck bolster. The C meant that the truck had a 9 foot wheelbase. The N meant that the journal pedestal-opening width (and I don’t have a clue what this actually is) was 13-3/8 inches. The S meant that the truck had roll stablizers. The 11 meant that the truck had 6" X 11" journal bearings.
I didn’t see any reference to the CIB in the article.