You picked the absolute worst British bike to break into electrical repair. The 71-72s had more wires than any two earlier bikes.....And the main harness is in two (or was it three) parts with a huge bundle of wires under the tank. OH well, too late for that. Now you have to hope that the parts are stock and no one has been hacking on the harness. If it's and original, consider a new one....or three, or whatever.....all new wires, if you are going stock.