I have been to a used hub cap store and there are a large number of different sized hub caps for GMC and Chev trucks. 1/2, 3/4, and one ton. They had all sorts in all sorts of shape and reasonable prices. Also the old "Moon" style hubcaps that are used on trailers now.
The lady at this store, (Edmonton Alberta), was very knowledgeble about what fit what.
I think most larger cities have stores like that.
But... old for them was probably no older than the '60's
Hope this might help.
Ter
