Just saw these on a 68 buick electra on C-list last night and thought how these might look good with a different center treatment.
'52-'54 Ford full wheel covers are cheap and they have a neat crest in the center. The Lincoln ones and the Olds ones that have been mentioned here are both personal favorites of mine and would be well worth the extra few dollars if possible but these would be a good budget option.
I like the 49-50 Pontiac ones too, but beware, some have a regular sawtooth outer edge to snap onto a standard rim but some have an inner ring that goes onto wheel clips like the old style dog dish cap and would need either a lot of modification or they'd have to be going on the Pontiac wheels. If you decide to go with those, be sure you're getting the snap on style.