Bill, I am an old school Mopar guy and have researched this in depth tonight. I have numerous books and actual dealer brochures. I have never seen this tire on a 66 Dart, but would swear I saw them on a 66 Formula S Barracuda in 66. The books show this as a possible "99" code, but the only 66 listing for an actual Blue Streak is for the 15" on the Hemi Coronets or Satellites. WO's and RO's. I remember the car distinctly, as I test drove it in 66. It was a Formula S 273-4V, four speed car. I believe the Blue Streaks were an option in 66, but only on the Formula S Barracuda. I worked at a Dodge Dealership throughout High School, (63-67) and we delivered many HiPo Darts and HiPo B-Bodies....but I never saw one with Blue Streaks. Not much of an answer....but I was there. It was a great time to grow up. I will keep looking.