If you are talking about central locking, then I have done this on my 63 wagon. I found the rear doors posed more challenge than the front ones. The central locking kit that I bought had steel rods that come up from the motors and clamp to the wires that come down from the inside lock knob thingy. The problem with the rears is that the lock knob wire is too short to clamp onto. I solved this by welding on a wire that sticks downwards so that I could clamp the wire on from the motor. Front doors were simple in comparison because the wire coming down from the lock knob is considerably longer.

The two front door motors incorporate switches so that either of the front doors can lock or unlock all 4. I haven't got it all sorted yet. The drivers door mechanism is a bit sloppy (being the most worn) so I can't quite adjust it so that the key can lock it. Not a problem, I just lock it with the push knob before I close the door. Just need to be sure I have my keys on me first.

Next step is to sort out the wear on the drivers door then add an alarm so I can have remote central locking.