Ah I'm coming to the party a bit late. Looks like Josh has you squared away though on what you should be doing.
I used a Blue Sea marine grade fusebox on the Busa. Powered that with a relay from Radio Shack that I tied into the turn signal circuit.
Right now I'm just running the GPS off of it. I need to wire up a charger for my iPhone, and ultimately the *sear your retina* driving lights I still need to hook up, and a full complement of heated gear. The Busa charging system will run all of that. Barely.
I still need to wire up a voltage gauge so I can keep a real-time check on charging status.