Not sure what "codes" you are taling about..... Build codes? Not "publicly"; maybe something that floated around in Design and Engineering but it didn't come out all over magazine articles.
I'm trying to remember what 'nickname' the original Mustang project group was given.... it basically had something to do with Iaccoca's ego and desire to "build his own car".
I'll have to dig around in The Cave and find my battered paperback copy of "Ford: the Men and the Machine". Pretty good 'biography' of Ford Motor Company, from Henry's first quadricycle and other early cars (including the first Cadillac, which was his design) through about 1985. I keep checking used bookstores and online to see if I can find another copy.