well! that did not go to plan, yesterday ive striped and cleaned the piston and the bore on my spare caliper and rekit it, all went to plan and easy, piston side in and out very easily now so I installed it in the car, all good until I went to bleed it, bleeder nipple was very hard to undo so I sprayed ferret piss (penetration oil) on it and left it for an hour or so, came back to undo it and the bloody thing snapped.
so, I thought I'll rebuild the original one, but thought ill spray ferret piss around the bleeder and leave it over night (spayed it about 10 times last night and this morning told myself just do little back n forth turns to loosen it up, did that for about an hour or so on and off, and the nipple started spinning in the on the thread (spins very easy by hand but does not move), now two calipers are ratshit, great! i hope the NOS not going to be the same being dry for 30 or so years
and for those who that will say i thought you put new rotors on, i did but i took them off so when I conneted the brake hose and bled the brake it wouldn't destroy the new paint on the new rotors