Looking at the wiring diagrams comparing 1970 with 1971, looks like attach the white/brown lead to the negetive pole on the ammeter and white lead to the positive pole. These are normally connected to the alternator warning light in the headlight shell (red light). Remove the warning light assimilator and jump between the green/yellow from the alternator and the white/brown (both were connected to the assimilator). This should give a negetive charge indication with the ignition switch on. When the engine starts the green/yellow alternator lead connected to white/brown will push the charge to positive provided the alternator is working.