Can you tell from the photos on Rock Auto what the difference is between the two trucks? Which one looks like the ones on your truck? It looks like you have a choice of 1" , 1.125", 1.375", or 1.5" bore for the cylinders.

Once you figure them out, you can rebuild them yourself or send them to this company for rebuilding:

Brake Materials & Parts Inc
800 Sherman Boulevard,
Fort Wayne, IN 46808
260-426-3331
http://www.brakematerialsandparts.webs.com/

Specializing in antique, vintage, classic, obsolete, unique and hard-to-find brake parts, bonding, riveting, rebuilding, drum and rotor machining, custom made brake hoses

1950 Chevrolet 3100 (Ol' Roy)

1939 Packard Standard Eight Coupe (The Phantom) | 1956 Cadillac Coupe de Ville (The Bismarck) | 1964 Ford Galaxie 500 coupe |1966 Ford Mustang (Little Red) | 1969 Pontiac GTO (The Dishpit) I 1979 Ford F-100 | 1976 Ford F-150 (Big Red) | 1995 Ford F-150 (Newt)