These are on ebay right now, and would be a nice compliment to those wheels, but they have the older center cap and art GM lug specific.
Looking at these more, there definetely is a different spoke pattern. There where two different rims.
Here's an ad from 1968, but I know the earlier ones had a silver painted center and the later ones had black. Don't know when they stopped making the ones with silver paint.
Can anyone else remember?