[StealthBird]

Well, what I was trying to say in the earlier post (not sure if I conveyed this properly) is that the 67 and 68 may have been within a car length of each other up to around 125-130 mph. At that point, the 67 may have taken another 20 seconds to get from 130 to 140 mph, while the 68 may have taken 13 seconds, thanks to the better aerodynamics.

The speeds quoted would have been at the limit of these cars top speeds back then, so I would imagine that the 7 extra seconds for the 67 model was all from 130 to 140 mph.