Here's a Crestliner wheel. Limeworks sells them.
Before you commit to restoring your Crestliner you might want to compare what you can "buy one done" for as opposed to what your restoration will cost. Plus, the time. The price of 50's cars is dropping each year as the market fades away. Parts are drying up and restoration costs are soaring. You will end up spending more money on restoration than what a #1 51 Ford convertible or Crestliner would have cost. For example:
https://www.carsforsale.com/1951-for...-sale-C1041074
Very seriously reconsider what you are contemplating.