I'll let John comment, but this sounds reasonable. Since the last recorded change to the 1968 AIM was on June 3rd, 1968, and the Bulletin references June 19th, 1968, it apprears that it just missed making the AIM by 2 weeks.
I'd like to see if we have other 1968 A/C cars in the database built after the June 19th reference with the clips. I don't know how long it takes from the release of a bulletin to manufacturing actually starting the process, but in this case, there's an actual date so I would say it probably occured as written.
Kurt, do we have any other late cars with A/C and the clips?
John, your comments please...