Here are a couple of pictures that were taken at the Marlboro Double 300 Trans Am races, Marlboro Speedway, Upper Marlboro, Maryland on August 12, 1967. Behind the Mustang of Jerry Titus, you can see the 1967 Ford convertible (Galaxie or Fairlane?) that must have been used to pace the race. The pictures were posted by Don Struke at the Historic SCCA Pro Racing Trans-Am Series Fan Group Facebook page.
You can see the 1967 Ford convertible pace car in front of the field during the pace lap of the 1967 Marlboro Trans Am race from :59 to 1:04 in this footage of the race: http://www.youtube.com/watch?v=0h9OLNQDxwk&feature=related
In addition, you can see a blue 1965 or 1966 Corvette roadster with two yellow flags flying from the rear being used to pace the field during a caution period from 5:07 to 5:10. I wonder why they used a different car.