Master cyl rod stuck
Or bolt it back together on the firewall with boot retainer back on the master cylinder, and hook up the push rod to the pedal. Squirt a little WD40 in where the "clip" is. Then grab the brake pedal and simply pull it firmly towards you to pull the rod out of the back of the master cylinder. The "clip" is actually just a rubber packer that holds the pushrod into the master cylinder piston. New ones are available from doctor diff.