The wiring, by far the most time consuming and also the most fun.
At first it seems like adding a few circuits would be no big deal, but it wasn't I found myself having to draw myself a schematic of the engine bay to keep on track. Attached is my current wiring diagram.
Before I started I made a trip to the pic-a-part to get a few needed items, buss bars from early 90's full size chevy trucks, and a 175A buss fuse and mount off an early 2k S10.
The goods, and man wiring stuff is expensive....!
Water proof relay and fuse panel box.
Wiring still needs to be loomed.