On my recent project, I built the entire wire harness and all the parts were done custom.
I had the 12V CDI with Regulator power to work with.
Repairing what you have is definitely gonna take less time and be easier. But, if you want something nice done once, I would just research the parts you need and build it all off the bike. Once everything is done, hook it up to power source and test it. Work out any issues.
If that goes well you’ll have the whole system you want and can take a weekend to remove everything from your bike, clean those hard to reach places, and put it back together.
I wanted to do LED but decided it wasn’t worth the extra complication. Unless you need more power for brighter headlights or some accessory, it might not be worth it for you.
If you’ve never done that, make sure you leave extra length. Especially on the handlebar parts. They have to be able to move freely, without rubbing or tension, from lock to lock.
Good info in there.