Probably better to rewire from scratch, its actually easier than butchering stock harness ( I just spent a lot of time on a Yamaha and ended up building a new harness as it was quicker)
If your running total loss ignition all you need is a kill switch, battery, coils, condensers and points. Get a couple of cheap automotive coils, they will probably be better than the 30+ yr old ones (you can use standard engine stop switch.)
Run a fused live to stop switch and back to one side of coils. Run other side of coils to ground through points. Make sure you have condensers in circuit and your done.
If you want to charge battery, leave generator in place and use only one yellow wire with half wave rectifier ( off an old ATV)
I'm pretty sure you can modify a C90/S90 rotor/stator to fit (or one of the Chinese knock off 110's)
Then you could use a really small battery and still have hours of fun
If you use standard rotor, remove the starter drive parts, saves a couple of pounds
PJ