It is when the clock is dropped that the pivot shaft for the winding mechanism can get broken off not during storage or use in a car.
The FA14 was the second series design for the Benrus and was used in 1957-58 applications you would want the first series clock for your 56. I have added pages to my site that show multiple views of the mountings (retainers) but I would suspect that what you have looks like this?
This is the shipping container for the second series winding. they made many more of them than the retainers to put them in the cars.
You could use a Moparmatic or desotomatic in your Adventurer either one would be correct and the mounting used on the 55-56 Desoto is one of the easiest to recreate and is shown on the bottom of this page. http://www.roadkillontheweb.com/mounts.html
Your clock is ready to operate with what you have but probably has nothing to hold it together (face to the mechanism) So often these are sold on Ebay as "fits it the horn ring button" and it does not without the special retainers.
Have you watched my Youtube videos about the clocks yet? they help explain things.
They are both on the bottom of the clocks page http://www.roadkillontheweb.com/clocks.html
or go to youtube and look for roadkillontheweb to find all of my videos.