Oh, that they could have been from a Shelby car never occurred to me. And no, I don't think that. They're Shelby brand slot mags and whether they are in any way connected with Carrol Shelby, I don't know.
If I understood the gist of the conversation on that other thread, I'd say that it may be unlikely that your wheels came off of a Shelby - but not impossible. It sounds as though they were used on '71 & '72 Shelby Europa editions that were shipped overseas.
The center caps seem to be chrome on the pics I've seen.