Went out and located one of each (67 Shelby and 67 T Bird wheel)
Here's a comparison for the major details. Checked both wheels - Both made by the same supplier - and neither had any dates on the rim or centers other that the large 67 on the face of the center section. Earlier wheels you can often find size and dating on the rim section. On later ones you can also often find a date (depending on year and supplier) dates on the rim and centers - sometimes coded
Center markings on the face (nothing found on the backside)
Year - 67
KW - Supplier
Ford in oval
Month (number of month) -(arrow)
Also notice that location of each is in a different order around and between the lug nut openings
Back side of center. Both were spot welded rather than rivet or edge welded like other years and wheels. Openings or non openings are shaped and cut differently. Comp and Shelby wheels have a larger and wider opening while T Bird cut outs and shape do not create a very visible opening if at all. On the one I took pictures of. Liquid poured on the area flowed through in short time (little or not light would pass through before test) while some held the liquid for 3-5 minutes before seeping through
Openings from the face side
Not very clear but this may be a picture of a comp/Shelby wheel from the late 60's. Appears that there is a visible gap as expected in the 4-5 o'clock area of the wheel
In going through my collection of pictures (yes slightly off thread
it was interesting to see that the car that was used as the prototype for the 67 GT500 appears to have not had the competition suspension or at least not the wheel and tires that came with the package.