I'm confused.

In '68 Mr Norms did a dealer conversion of 383 cars to 440, Darts only. Then in '69 the factory did it. 5th digit is M, Darts were GTS, Barracuda was coupe or fastback in a 'Cuda 440 package. All were automatics.

I knew a guy back in the 80's that had a true Mr. Norm GSS Dart...

His nephew had an original M code 69 Barracuda...