The lights, coil and horn should all be changed for 12V items. Make sure the new coil is connected the right way round: the "-" terminal should be connected to the maroon wire that goes to the points (assuming negative earth)

There's no need to change the condenser if you are sticking with the Wipac points ignition.

If you wire the system for negative earth, then you can use widely-available LED bulbs

I tried two different LED headlamp bulbs. They were nice and bright, but both failed after a few months due to the cooling fan breaking. I'd recommend only using fanless LED bulbs. I have since found that the alternator has enough output to power a proper 55/60W H4 halogen, so I just use one of those.

If you are using negative earth, then don't forget to swap the wires to the ammeter, otherwise it'll read backwards