i've received replacement rotors, bearings and seal to address the 50 year old Kelsey Hayes worn rotors. Upon caliper removal and pad removal, i noticed the caliper pistons were stuck. the inboard pistons would not expand. i noticed some rust around the rubber boots, but boots not torn. after further reading and some youtube video searching it looks like my old calipers need some upgrading. is it worth the effort and trouble to rebuild 50 year old calipers with new piston, seals, crossover tube and bore hone? i was able to expand all pistons finally using some blocks of wood to hold the pistons and press the brake pedal a few times. i havent disconnected the brake hose yet or removed a piston to look for internal corrosion. input appreciated, thanks.