You only need to route one wire and the best way to do that is using the spare Y/R (foglight) wire in the bonnet plug. It is not heavy enough but easliy desoldered and replaced with a thicker wire. I wrote up the instructions for the complete installation here:
All wiring/relays/fuses are in the front bonnet. All you need is a high capacity wire from pin 6 on the bonnet plug to the B+ (big brown wire) terminal on the alternator.