Front brakes binding

[rstucke]

Just add that master cylinder and booster look original

could be 
brake pedal return spring - does the pedal arm hit the bump stop under the floor when released, if not the transfer port in the Master cylinder may be covered slightly stopping fluid returning. push on the pedal let it go listen for the thump under the floor

spring in the blind end of the master cylinder collapsed - same outcome as above. Would need dismantling

central valve in the booster intermitantly leaking allowing atmospheric pressure to one side of the diaphragm (they are vacuum suspended ie. vac on both sides when not in use) - unlikely but may be caused by push rod with not enough clearence, diaphragm spring busted or valve problem. unlikely because front and rear would bind.

Don't think it's hoses or callipers because unlikely both would go the same amount at the same time

I think Andy has covered all this and given you a number of things to try