For the pure ease of installation, the 235 would be the best. Get one from a '54-'62 (excluding '62 Nova) car or truck. Patrick's or Stovebolt Engine can help with information on the swap. You may consider a 261 as well. It'll bolt up the same as a 235, just has a larger displacement.
Welcome aboard the 'Bolt, let us know how it works out on your '50.


Bill Burmeister