Kelsey Hayes 4-piston calipers

Rebuild kits are available from virtually EVERY parts store on the planet. Pistons, too. Pad retaining clips are available new from any Mustang resto supplier (yes, I said Mustang).

BUT, you need to look at the kits and your calipers. Being a 67 you should be good with any kit, but there were two dust boot types. some kits come with four of each, while others only seem to have the early boots (which your car should have come with).