Hy campbell45, it is very common that the bore for the clutch side of a hydraulic clutch/ brake master be smaller on large trucks as the trucks usually have multiple wheel cylinders to supply through the brake side of the master cylinder. Some research revealed that the standard master cylinder (1 1/4" bore Raybestos p/n MC36212) is no longer being reproduced, the heavy duty master cylinder (1 1/2" bore) is available through Napa as their p/n NMC P55385 $79.99 + $37.14 core charge. I'll check on the wheel cylinders and get back to you.
