no reason to run extra wire if you wont be having an HO alt.. just buy extra batteries for the rear and 1 maybe 2 runs of wire would be enough.. the wire doesnt make power it just transfers it and you really have nothing to transfer from the front to the rear.. only reason i see you having more than 1 run is if you have a battery bank in the front and you need to get all that power to the rear
a good battery charger is going to be your friend and you will need nightly charging.. the only thing that sucks is once your batteries are low they are low and you cant bump till the stock alt recharges them back up, or you put them on the charger so still out of luck.. sort of like a lowerider once the juice is gone its gone