Try our new info resource - "Aladdin's Cave" (Main menu)Just added a separate link to Ash's Dropbox thread (shortcut)
If you want to go back to standard any 72 onwards 500 or US 550 K0-K2 will fit but the US 550 has a "Safety Interlock" module to stop the starter working unless either the neutral light is on or the clutch lever pulled.A 550 K3 loom will fit the switch you have and probably the handlebar switches DEPENDING on the type of starter button you have