brake problem

Is the master cylinder the correct one for the drive train you have? I had the same problem with a truck I recently bought. The previous owner put a 86 D150 body on a 77 W200 drive train. The master cylinder for the D150 did not have enough volume or pressure to fully operate the brake system for the W200 drive train. I figured this out the hard way thru process of elimination and it cost me a lot of money. Needless to say I have all new brake components on that truck now and not because I wanted to.