If you used the disc brakes that came as an option for the first time in 1967 then they supplied you with the same four piston fixed bridge Girling disc brakes as used on the Corvette. You can buy all of the parts except the machined steel wheel bearing hub that was used (it is not reproduced) new from your auto parts store. These cars also had 15 inch Rally wheels made by Kelsey-Hayes. Kelsey-Hayes is still in business and sells OEM reproductions.
If you wish to retain the a 14 inch wheel you will have to buy the wheels off of a 1969 Camaro or a 1969-7'2 Chevelle that came with the optional single piston floating caliper disc brake. If you want bigger brakes than the stock 11 inch rotors (keeping it in the 12 or 13 inch rotor) then you will need at least a 16 inch wheel. Steel Rally wheels with trim rings and hubs are reproduced in 16 inches to clear a 13 inch rotor and caliper.
Always buy your brakes as a matched kit from a brake company such as MBP CPP that resell packaged stock parts (though not always made in the NAFTA area out of quality parts). Or you can buy from an aftermarket supplier that makes everything themselves in house in the US machined out of billet stock such as Baer or Wilwood that got started originally only selling bigger brakes to NASCAR, but later expanded into the muscle car market. Master cylinder piston diameter, push rod length, recovery port location wheel cylinder and proportioning valves all have to match. Get one off and either the brakes do not work or they lock up which is a definite safety hazard.
I have used SSBC, Master Power Brakes, Wilwood, and Baer brake products on my past builds, and I have been very happy with the results. Master Power Brakes sells a kit that looks like the original factory build that requires the use of 15 inch Rally wheels (any 15 inch wheel should clear but you have to worry about the spokes on a cast aluminum mag wheel sometimes not having the clearance you need).
SSBC sells a kit that uses the two piston PBR caliper,
or the stock GM single piston brake:
Wilwood offers CPP parts on their cheaper kits, so CPP apparently meets Wilwood's quality control inspection procedures (which sometimes are nothing more than free replacement of defective parts if you live long enough to make a claim). I am not knocking CPP a lot of people use this product, but I got out of building cars before I became aware that they even existed; so I can not make any claims about whether they make a good product or not.