I have four center caps that came off the stock steel rims from a 79 pickup I had. Not positive if they're common or if anyone wants them. They aren't mint but in pretty decent shape. Let me know if you want these. The $20 bill is for a size reference.

 

Tidbit of info for Toyotaholics, they won't fit the similar era 4 lug car steelies. Trucks have a larger center bore. Should fit any stock truck steelie though of the various eras.