you actually have a one wire alt, the big post on the back, the side connector [DA plug] has 1 wire [red] to the main terminal on the back of the alternator [BATT], the other needs to get a ground [usually via an indicator dash light] only when the ignition is on, with it hooked to the BATT terminal also it's powered all the time, causing the drain thru the alternator - [edit] you could run that wire to the fuse panel switch for the ignition
you don't necessarily have to de-power the panel to change a fuse, but not doing so could be a hair-raising experience
I'd use a 10ga wire from the battery to the fuse block, no matter the route, although with no fancy electrical things a 12ga should work - if you have a soldering iron and some heat shrink tubing you could splice a couple shorter pieces to get the length you need
Bill
