Thanks Guys!
I started restoring the hubcaps a couple days ago. Here's my progress so far.
For the chrome-like portions of the medallion I used a product from Spaz Stix called Mirror Chrome. This product is used in the R/C car hobby to emulate chrome on R/C Car Bodies. It is designed to be applied from the back so it produces a finish which is close to that from the factory.
http://www.spazstix.com/whatsnew.php?id=16 This is what I have to start with. All 4 are about in the same condition. The disks are in good shape; all I need to do is re-do the black stripes. The medallions are a mess but free from major cracks.
Step One:
Remove the spring ring holding the medallion in place. Using Easy Off Oven Cleaner (yellow can), remove as much of the original paint as possible. I got 99% of it off on the medallion below and I got lucky. The black paint in the "Three Hundred" grooves did not come off on this one. I won't be needing to get out the magnifying glass and the fine brush.
Step Two:
Paint the Red, White and Blue stripes on the back side of the medallion:
Step 3: Prep the surface using Spaz Stix aerosol plastic surface prep. Allow to dry per the instructions and shoot the entire backside of the medallion with Spaz Stix Ultimate Chrome (aerosol), applying several light coats until covered.
Can't do much about the crazing in the plastic. These are over 45 years old after all. The reflective properties of this paint are very good. I am expecting even greater results when I shoot a top coat of black over the Ultimate Chrome. Overall, I'm very pleased with the way they came out.
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just stunning! A real piece of art. 
You did a great job! I used my 65 New yorker as a party barge as a teen and miss those cars.