The C body and hemi had similar MC in certain years. What is the casting number of your MC if it is bendix? The primary piston sticks out of the rear of the master cylinder some. So when assembled it will push in. The key is that the "compensating holes are not covered by the pistons in the static position. Once you start applying brakes those holes are closed by the piston seal. If they are closed in static position pressure cannot bleed off when you release brakes.