How do you change the brake master cylinder on a 1967 Ford Mustang?

disconnect and remove brake light switch from pedal

slide the pushrod and washers from the pin, ( on the single cylinder models just slide the rubber boot back on the master cylinder so the pushrod will slide free when the cylinder is removed )

Remove the brake line (s) depending on whether it is a single or dual, and plug the pipes and holes, take care to catch all the fluid that will come out.

Remove the screws ( bolts ) holding master cylinder to the firewall

Pull the master cylinder forward and pull up to release it from the car.

Install is reverse of removal, then bleed brake system.