I have a core booster. It would have to be rebuilt. I send them to a guy in CA, brakeboosters.com for rebuilding/replating.
Its now Booster Steve and has been for 2 years . Admiral Dewey retired and Captain Steve runs the ship! Tell him Eric sent You. 503-238-8882
Do yourself a favor and upgrade to a 67 booster and dual MC combo. If you have a floor shift clearance between the larger booster and steering column isn't an issue. I bought a used set and sent it through NAPA for rebuild.