You can check around on this site and get a lot of help.
If I look in the Shop Manual it seems you have the same brakes as I do on my 59 Viking, but mine is a 60 series.
I asked around here and got advice to check with alretta truck parts.
Mailed Geoffrey there and he asked a couple of questions. After that I ordered both a new Hydrovac unit and a new master cyl.
Next year I had to replace right rear wheel cylinders and also bought adjusting kit from him.
He has everything you need for sure, just mail him and ask.
http://www.alretta.com/Br /Ulf from Sweden.