Thanks, my rigs coming along but slowly. Hopefully I can get back to it here soon. Been building barns this past year.
My rig hadn't run in close to 20 years at least, so I know what your going through.
You may be able to get completely new cylinders from your local NAPA. MY 47' currently has a 54' rearend under it and it has a leaking wheel cylinder I plugged for a quick repair but NAPA is supposed to have it.
Jim carter carries new wheel cylinders and rebuild kits for the big trucks.
http://www.oldchevytrucks.com/cart/index.asp?cat2=10225&path=1947+-+Early+1955+Truck+Parts%2FMechanical%2FBrakes%2FWheel++Cylinders+and+Repair+Kits
And this place can probably help to. I ordered a new Hydrovac brake booster through them cause mine had failed, it's called Alretta Truck.
http://www.alretta.com/Good luck
By the way you got yourself I nice looking rig.