GTS or GSS

Well this is starting to make some sense to me. A buddy sent me pics 5-6 years ago of a friends 68 dart and swore it was an M code. I told him that only 69 were Mcodes. I was wrong...again.
I cant remember if he sent me a pic of vin or fendertag with the M in it.
Would M be in fendertag for 68 or 69?
Good question. M code is listed in my Galen books a "special order" for 68 and 69. There are 48 LS23M8B 440-4 68 Dart GTS's listed as " Mr.Norms GSS". No Mr. Norms GSS's listed in 69. No other 440 powered Darts listed for 68.