I used late 1960's C-50 /60 wheels cyls on the fronts of my '55 series 4400; the original 7/8" bore cyls are long,long obsolete.
Turns-out the only difference between the '55 front WC and the later ones are the brake hose connection; the '55 cyl comes straight-out of the wheel cyl (parallel to the axle); the later cyl has the brake hose thread in at an angle. It worked just fine on my '55...the flex hose is long enough to accomodate the change without stretching or kinking.
Stay with the later (Bendix) brakes...the fronts are 14 x 2, and shoes are still available (#109?).
If it has the 15 x 4 rear brakes, the shoes would need to be relined, but wheel cyls are stil available.
I got all new wheel cyls for my '55 about two years ago, for about $150 from my local Mom'n'Pop jobber.
1951 is the change-over year from Huck to Bendix brakes...Huck brakes work okay, but if you're building a working truck, the Bendix brakes are a lot easier and cheaper to maintain.
Good luck !
