Mark,
The part numbers for at least 67 were sent out to dealers at some point in a memo or bulletin, not at all sure on 1969. It listed the manufacturer and an ordering procedure with part number (I believe the manufacturer part number not a GM one). Somewhere in my piles of GM and dealer paperwork I have a copy but have as of yet not been able to lay hands on it again. If memory serves it was put out sometime after the end of the IPC order deadline for the replicas so dealers could order their own and add the decals later. They may have had a similar notice to dealers after the 69 run but if they did I have not seen one for that. I know it is not much help to you now but if I find it I will post it up for you, if nothing else it gives you a time range and area of docs to concentrate on. The numbers have never as far as I have seen been listed in any US or foreign parts book, assembly manual or supplement though that does not mean one did not go out.
Mike