The simplest thing to do is run a long large wire < size depends on lenght and amps> to the batt B+ or the batt side of the cut off switch, I am assuming your batt is in the back, the larger the wire and the better the quality will determine voltage drop from the alt, care full wire routing and chafe gear is important , fusing the output wire is up to you depending on how safe you think the run is and the wire used, proper crimp ends and shrink tube is a good idea, I always run agw wire one size larger than the chart recommends and never had low voltage problems, this is the basic simple stupid way to do this, there are many other ways to wire this system just look up the posts