power or manual brakes

a booster needs 14" vacuum minimum to operate. if you do consistent braking, even 14" is not enough, you will get a hard pedal within 4 stops. if you run a smaller bore master(15/16" or 1") you will get better pedal feel on manual brakes. I have a 360 in my 68 cuda with manual discs and can stop on a dime. if you still want a booster, you can run an extra can or an electric vacuum pump, but they add bulk to the engine bay. you will need a donor master for the pushrod and rubber retainer.