On my c25 1967 I had the same problem with the interior lights. In the end I re-used all the old cables, exept for one Interior light on the roof, Eventualy i put the cable in a strip of wood 10mm thick, 20 mm wide,attached to the roof. When I have more time, I will throw it out, and put in a spotlight on the wall, shining at the roof. That should look good!
The other lights I can't help you with, they all worked properly.
good luck!