Converting from drum brakes to disc requires changing the master cylinder as well. The disc brakes require a larger master cylinder bore to deliver the additional fluid required by the larger pistons of the calipers versus the original wheel cylinders. But even disc-brake master cylinders are not a one-size-fits-all situation, so the Baer system includes a GM-type unit spec'd for the application. Note that the master cylinders used with manual and power brakes are not the same. Though a power-brake master will physically bolt directly to the firewall of a GM car, the pedal pushrod will not properly engage with the master-cylinder piston.