According to the 1967 Master parts catalog, Ford had an early and late wheel for Mustang, Galaxie and Fairlane. Before and after 9/26/66. This includes all wheels, woodgrain or color. The first woodgrain wheel was a C7OZ-3600-R. The later woodgrain wheel a C7OZ-3600-S. At some point after July 1968 (the last Master Parts catalog I have before the 1975 Final issue), Ford replaced the C7OZ-S wheel with either the C7AZ-3600-U or the C7OZ-3600-AJ wheel. The AJ wheels were complete and ready to bolt on with the rings, plates, screws and cam missing only the center pad. The R and S wheels were wheels only and did not have any additional parts. I know the C7OZ-AJ wheel had thick spokes as we used to have pallet loads of them in the 80’s. We sold them by the hundreds into the early 90's until they were gone.
I would caution not to jump to conclusions as these wheels were NOS in the Ford boxes. It would very easy to imagine that most of the nice condition thick spoke wheels still on cars are probably these wheels. You even see them come up for sale every now and then, still in the box with a COD tag with our Michigan address. My point is that a car today may have an original Ford thick spoke woodgrain steering wheel but it may not be the wheel that came on the car from the factory.
Regards,
Scott