Yes and many will convert the whole electrical system over to 12 volt which opens up many other parts sources and choices since the 1956 cars and trucks were the first Fords and Mercury's to go 12 volt. I had a 1954 Customline and was quite happy how it worked on its orginal 6 volt system as long as you have the engine tuned good, with all the proper sized wiring (needs to use a much larger gauge than 12 volt systems) and all the wire termanials are clean and tight they can work great. But mine wasn't a car that I drove that much but if it's something you plan on driving a lot than some up grades are nice to have. Note that lots of cars & truck with the vacuum wipers only used the engine vacuum for the wipers so they will work without the vacuum booster pump too, just not as well.
One other thing you might try is putting an add in out the sires For Sale, Wanted, & Trade section of the forum all the way at the bottom. Maybe someone has a good used fuel pump core they took off that you can get for the Diafram out of it, this same fuel pump with the vacuum booster design was also used on severial other Ford & Mercury cars and truck engines both six and V8's of around that same era, as well as for some other car and truck brands too. IE would use the same Fuel Pump Body and all the internal parts are mostly identical with the exception of their useIng a different lever shape or lenght to fit into the different engines. Do they have any reasonable universal 6 volt electric fuel pumps in your erea? If not your right it puts you in a tough spot to be able to do it on the cheap for now. Best of luck
Edited One other thing if you wanted to try and could find the proper type rubber material you could even make a ne diafram too with some simple hand tools like leather punches.