Thanks! It just got still more interesting.
According to press information, the last production day before the Christmas break for Newark was Friday, December 21, 1973. The door sticker has an MDH value of 122014, which translates to December 20, between 2 and 3 PM. So your car is one of the very last C-bodies to have ever been assembled at Newark, because from January 1974 on they only made A-bodies. Remember that C11 on the fender tag is just a scheduled production date, the actual production date is revealed by the MDH = "Month-Day-Hour".
And another reminder: PH41M4F152371 is not one of the highest VINs, as many people are inclined to think when talking about "last so-and-so". The highest VIN I ever found for 1974 MY Newark-assembled C-bodies is PL41K4F159564, a modest Fury I.
Considering the unrestored condition of the car, you may even get lucky and find a broadcast sheet with still more info. The easiest place to look for one would be under the back seat.