I can neither confirm nor deny this story, but I supposedly met the designer of the billboard stripe at the Barrett-Jackson auction in 1995. His name is Tom Hale (not to be confused with former head-of-design and fellow AAR owner Tom Gale), and he has created the event poster for the BJ auction for many years. He told me that in 1970 he was working in the Chrysler graphic arts department. He had created the AAR stripe and some other stripes, but was bored with stripes and wanted to design cars. While he was waiting for a departmental transfer his boss came to him and told him his next assignment was to design the stripe for the 71 Cuda. Tom was pissed and in a fit of rage he drew a stripe that covered the entire back half of the side of the car. He submitted the artwork and thought, "if you want a stripe I'll give you a f@#$%&g stripe!" To his astonishment management took the stripe seriously and it was approved.
If I recall correctly, Tom got his transfer and designed the tail lights for the Duster/Demon and the 1972+ rally wheel center among other items.