Seems like they changed the cars and their numbers for every race. I have an article on the 1968 12 hrs of Sebring were Yenko drove a red white and blue 1968 L88 Corvette wearing the number "2" co-driver was Pedro Rodriquez. Smokey Yunick had a Trans Am Camaro there that had a lot of trouble getting through tech. After finally passing tech it set the 13th fasted overall qualifying time with a 3:01 lap. Mark Donahue had second fastest Camaro time with a 3:02 and Don Yenko was fastest Corvette with a 3:04. The Camaros were quicker because they could fit bigger tires then the Corvettes. This is from Corvette News Vol 11 No.5. The same issue had the article where Don was testing a 68 L88 for LeMans. Pictures from this testing day.
