I would leave the wiring alone for now and install the winch make sure you secure the large cables to the winch so the insulation doesn't rub on anything. Then see where it goes, I have used the snot out of my winch and the stock wiring to the alternator holds up fine, as a matter of fact the later stock alternator keep up fairly well if you keep revving the engine on long pulls. When doing trail repair work and building a rock garden as well as pulling trees to block bypasses we used winches for long periods on end till the got seriously hot, yet the charging system kept up enough to not deplete the battery or make the charge wire to hot. So just try it as is, I am pretty sure you will be fine. Oem wiring is often better than add ons