I'm pretty much decided on making the box pictured above into a combination power/storage box.
I am going to divide the box into 2 sections. 1 side will house the battery and the fuse box, perhaps my power inverter as well. The other side will be used for storage.
I am going to keep the 4 wire harness for now, as I don't have brakes on the trailer. On the truck side, I will be running a 0 AWG wire from my battery to the rear of the truck where I will place a distribution block with an ANL fuse to a 4 AWG wire capped with an anderson plug. I am not running a ground from the battery to the plug, I will instead ground the anderson plug at the rear frame. On the trailer side, I am going to run an anderson plug with 4 AWG to the battery, which will also have a fuse. What is the proper way to ground at that point? Do I run the anderson to the battery? To the frame of the trailer?
I am going to use the rear anderson plug on the truck to power the winch as well, when needed back there.
Any glaring issues with my plan?