The 48 Mr. Norms 440 Dart GSS's were indeed M-Codes. I know of 14 of them that I have personally seen. Indeed PlyMOUTH put 383's in A-Body's before Dodge did. Mr. Norm was a Dodge dealer and couldn't stand the fact that PlyMOUTH did it and Dodge said it wouldn't work. Norm had to put one in a 67 Dart GT, drive it to the headquarters, and beg them to make it! That happened late in 1966 and by February Dodge started building the 457 Dart GT+S cars we know about today! He had to show ALL of Chrysler how to put a 440 in an A-Body...