510/1600 Rear Door Handle Conversion
Remove Latch tabs and circlips from original handles
Tap latch pin out of donor handle using a punch
Cut bracket away from the handle so you can use it as a template (using a 1mm blade and an angle grinder, or a hacksaw)
Tape up chrome on new handle to avoid damage
Use template to align where the new hole needs to be drilled
Setup handle in vice
Drill through new handle using the template as a drill guide.
Use a 2mm spacer or some cardboard to avoid crushing handle mechanism and press latch pin into the hole just to get it started with the vice.
Remove from vice and tap with a hammer until the pin bottoms out
Install latch tab and secure with E-clips