I am not 100% sure which tire supplier was being used at that point in time for the SS, but I know that Firestones were used on some of the early cars in the 68 model year. My Dad's 68 SS he bought new in November of 67 had Firestone redlines on it. Somewhere around here I have some pictures showing the car when he bought it new and the Firestone can be seen in the sidewall. He removed the factory steel wheels within a few days and replaced them with Cragar G/T's but he had the factory redlines mounted on them. Come to think of it I have a complete set of wheels with original white stripe tires from a drum brake 68 that was a February built car, and I think they are Firestones or Uniroyals, not sure, but I'll check them tomorrow.................Maybe some of the others can chime in........................RatPack.............