That looks like original Kelsey Hayes booster and master for the 67-72 fixed caliper system.
If so, the same master was used with or without booster and is now very hard to obtain.
You can check the casting number against Brad Schroeder's list of M/C. Its posted here, moparts, and probably a few other places.
Nice thing about the booster is it places the initial pedal position lower. Whether you like the feel of the booster is a personal decision.