https://bringatrailer.com/listing/magnesium-spline-drive-wheels/
I have used these original American Racing wheels on CSX 2401 intermittently for about 30 years. They were an option from Shelby American and listed in the Shelby parts book.
I now use chrome wire wheels and don't have space to store these anymore. See the ad for more information and photos. These are probably the rarest of all American Torq-Thrust wheels, with the spine drive version thought to have been specifically made for the 289 Cobras.