Which 7/8 master cylinder?

AJ/FormS said

You loosen the M/C from it's mount, and withdraw it from the mount. This relaxes the pushrod, and allows the internal spring inside the M/C to push the piston back into the parked position, and that opens the C-port, and that allows the fluid to return, unlocking the brakes...

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A bit late, but I see this a lot. Why would one need to "relax the push-rod"? There should be nothing preventing the brake pedal from swinging freely as far as the MC piston wants to move it, i.e. no "unbolt from firewall" required. If the pedal is bottoming out on the brake lamp switch, that is wrong. Unbolt the switch until the brakes are installed, then adjust the switch to sense, but not affect, motion of the brake pedal.