changing the M/C in my 68. Powr disc rr drum. bought a master from auto zone. Not the same one. New one is short and wide and the one on the car is taller and thinner. Checked year one's site and found the new one is for a 69 not a 68. I guess the real question is will it matter?? They physically bolt up and the lines fit. Will there be a brake travel problem, etc.???

Joker.

Brake pedal travel will greatly depend on the bore diameter. A smaller diameter gives more travel. Compare your old and new one.

Mind the front and rear reservoirs. The disc reservoir should be the larger one.

Rob