hey all, ive got a 1ton k5 with 4wheel discs on 42s. originally i replaced my stock master cylinder with one off a k20 but that was still inadaquate. so i went to advance auto parts and started looking up master cylinders of various truck. im actually going to start working there within the week, and i know everyone so they didnt care if i ordered and then returned them haha. i wanted the p30 one, but i dont have hydro-boost. then i found it! it actually looks bigger than the p30 van master. Part Number 102754, its off a 1999 c3500 with 4wheel disc. i just installed it, (the lines are reverse) and wow what a difference, i cant even press the pedal to the floor anymore, and can lock up if i want to. just thought i would share my findings, as i know alot of people are looking for the perfect solution after goin to 1ton with discs.