servo

My brake servo isn't working, as evidenced by the brake pedal test and having to press really hard on the brake pedal to stop the car. Having stripped down the servo the only thing I can find that may be the cause was the air valve piston which was stuck in the bore of the slave cylinder...

Hi, my mechanic says it needs to be replaced. Any idea where I can get one? He says it's a Lockheed cylinder. Mine is a P6 3500s from 1973. He also suggest to replace the master. Is this advised? Thanks