This was the decisive tip-off:
Using another search interface I found an article by Louis M. Heldman entitled "Chrysler’s Jefferson plant gets a new life" (Detroit Free Press, October 31, 1978, page 16). It reports on the start-up of truck production at the plant. There it says:
"The plant produced its last cars on June 24, when Chrysler Corp. ceased production of the large C-body Newports and New Yorkers it was building there."
So we should look for cars whose MDH starts with 0624.
If you would ever like to make a day pass like 5 minutes, I'd caution against this. Unfortunately you have to be there in-person:
Detroit Newspaper Search | Detroit Public Library
...
Keywords I'd search for within the month of June would be "Chrysler, Jefferson, New Yorker, layoffs, UAW, Plant Manager, retool"
Using another search interface I found an article by Louis M. Heldman entitled "Chrysler’s Jefferson plant gets a new life" (Detroit Free Press, October 31, 1978, page 16). It reports on the start-up of truck production at the plant. There it says:
"The plant produced its last cars on June 24, when Chrysler Corp. ceased production of the large C-body Newports and New Yorkers it was building there."
So we should look for cars whose MDH starts with 0624.