Our Hydropower hydraulic brake assist power booster fits 1955-59 Chevy and GMC trucks and generates up to 1800psi of line pressure to the brake calipers. It is fitted with a POL master cylinder and proportioning valve. This kit is powered by hydraulic line pressure from the power steering pump. Frame clearance is equivalent to a 7" diameter vacuum booster. The frame brackets are correct for 55-59 GM truck floor mount applications. The average power steering pump puts out from 800psi to 1400psi line pressure. The Hydropower® uses this to convert to pressure to apply against the master cylinder. This greatly improves stopping performance and driver feedback. These hydraulic power boosters can be easily installed on an existing vacuum booster vehicle or used to convert a manual brake setup to power with ordinary hand tools and average mechanical ability.