[tom406]

This would be a neat discovery. Very much like the 15" wheel option on '67 Mustangs. A few hundred were ordered with the "Sports Suspension" and basically you got the Shelby suspension and 15x6 steel wheels, and Thunderbird full wheelcovers. Or a precursor to the next year's Yenko 9737 package with the Z/28 rims and tires.

I just saw a set of "big letter" DF's, and they only had DF by the valve stem, and the date (Dec '67) was stamped inside the hoops (the area hidden by the tire). You may have to dismount the tire to see the date if yours are similar.