Remove the booster and rod that goes to the pedal. Bolt your master cylinder straight to the firewall. The threaded holes are actually in the pedal support. Use two remaining bolts to attach the pedal support to the firewall.
Use a master cylinder rod for 65-66 manual brake car.
You can reuse the original master cylinder for your drum brakes. You will need to reconfigure the hard line to the distribution block.
Plug the vacuum source at the intake manifold on the engine.

Be sure the rod cannot pull out of the master cylinder when the pedal is pulled up towards the driver seat. Manual brake pedals have a lever at the top that hits the pedal support, limiting upward travel, to keep the rod from pulling out. Some power brake pedals did not have the lever at the top since it was not needed. If yours does not have the lever, you can weld one onto the pedal.

If you want to install a dual piston master cylinder, the 67 Mustang drum brake version will work. Front port goes to rear brakes. Rearmost port goes to front brakes. Use SAE inverted flare plug to plug off the distribution block rear line fitting and connect that rear line straight to the master cylinder front port.

Why not just replace the booster.

rustycarr wrote:

Thank you.will the 67 MC still work when i go to  front disc 

You will need to change to the 67 disc/drum MC when you install the front discs.  I ran one for years...worked fine.

MS wrote:

If you want to have authentic GT350 appearance, you can change to the 65 disc brake master cylinder. It is single piston and will work with either type brakes.

good idea, thanks for all the great info.