Ignition System

Spark Plug NGK DR8EIX or DR8ES

Rectifier

The rectifier can be easily replaced with a rectifier regulator, which makes everything more reliable and makes the heatsink resistor redundant. See wiring diagrams

Apparently a CB350 stator - gives 12 volt system.

But there seems no point swapping as the alternator will output 12v provided there is no 6v component in circuit to limit the supply (including coil).