The 56 Merc Turnpike Cruiser or Phaeton model like yours has the same windshield height as the 55/56 Ford Crown Vic and the '56 Victoria's.
All the major resto parts suppliers sell wiper blades for the Crown Vic in 11" and 12" long in either bayonet or pivot pin styles. all you need to do is determine which connection style you have.
They don't offer much in the way of wiper blades for the sedan & wagon models unless people are just removing what they currently have and buying the entire set of wiper arms and blades for a Vic to use on their sedans. Hope they don't drive in the rain much. I do, so I opted for the Trico cutoff blade refills to use on my existing wiper retainers.