This truck should have two master cylinders on it one for the inching(left brake pedal) and one for the service brakes(right pedal)......which one(s) did you check?
The brakes shoes on this truck are internal to the axle assembly so is a little different doing a brake job on this truck...the Parking brake is a separate drum on the Transmission and is adjustable....if the shoes are still in good shape that is??is just a small five inch diameter drum that you should be ale to find if you follow the park brake cable down to it