Howdy. Thought I'd share this super simple install for anyone else looking to organize their electrical accessories and clean up their wiring. Thanks to several members of this forum for inspiration.
I purchased the Blue Sea 6 circuit fuse block with a negative bus, in order to keep all of my wiring as clean as possible. I installed a 100 amp circuit breaker in front of the fuse block.
I made a mounting bracket out of a small piece of sheet steel. I first bent the steel to fit in the spot just behind the factory fuse block, using the OEM mounting holes above the wheel well. The angle is slightly more than 90 because the mounting location is angled outward just a bit. I used a heavy hammer and a block of wood to bend the steel - not perfect, I know, but cheap, quick, and effective if done carefully. I cut the bracket to size, and drilled holes to mount the bracket to my truck, and also to mount the fuse block and circuit breaker to the bracket.
I cleaned up all the holes and cuts with a file, and then sanded the whole piece smooth. I primed the bracket and then painted it with Rustoleum Gloss Black engine paint.
I installed the fuse block and circuit breaker to the bracket using 3/4" machine screws, with washers and lock nuts.
I attached the completed bracket assembly to the truck using the OEM mounting holes. (The OEM holes accept M8 1.25x25mm screws).
Next up was the wiring. I measured and cut 4AWG wire, and crimped and soldered on copper ring terminals. These all got heat shrink tubing, and I used red electrical tape to denote the positive leads. Then it is simply a matter of wiring it all up. Run a wire from the positive battery terminal to a terminal on the circuit breaker. Run another wire from the other post on the circuit breaker to the positive post on the fuse block. Finally, ground the fuse block by running a wire from the negative post on the fuse block to the frame (I used the same bolt as the battery ground). (This is only necessary if you are choosing to run a fuse block with a ground bus, as I am). I ran two of the wires underneath my mounting bracket to keep things neat.
Only had time today to pug in my bed lights to this, but it will be almost full once I get around to moving some other wiring to this block.