I've seen the M as the fifth digit on every 440 GSS I've ever seen. The maroon, silver and black cars from one collection and the two matching yellow ones from up north.
48 of them, all sold at GSD I believe, exclusively.
OK...to get this thread back on track,,,you're saying that 1968 Darts were shipped to Norm's dealership with an "M" in the VIN? What engine was in them when they left the factory...383 or 440? Everything I've ever read or heard says there were no 440's ("M") in Darts in 1968, so Chrysler didn't install the 440 in those 1968 Darts.
So who installed the 440 in those cars...must have been Norm, right?
Now, if Norm did it AFTER they were delivered to his dealership, how did Chrysler know which ones he put a 440 into (so they could attach an "M" code VIN)?