Incredible write up. The pictures helped tremendously. With that, I have a couple of questions:
I'm tracking the 16ga wire from the seat warmer fuse in the fuse block to power point 85 when the ignition is on, but I missed the 18ga wire from the battery that you ran with the starter cable to the circuit breaker. Where exactly does that go and what does it power??
the starter cable is actually 4 ga and goes from the battery, to the circuit breakers, then on to the service stud on the fuse side of the relay box. It is shown in the 5th picture down (the real world schematic). The 18 ga wire is your switch and illumination lead for the switches to control the relays.
Additionally, your picture of the backside of the block is great for the relay wiring(that includes the accessory and the switch), but do you have one that depicts the wiring for the non-relayed connections?
so... on that same schematic I mentioned above, see the 14 ga wire that I ran between the fuses and relays? You just run wire from the fuse directly to the switch then back to the terminal block instead. That is why the wire I ran inside the cab was 12 conductor - each non-relay switch takes up 2 of the conductors, the illumination takes a conductor, and each relayed circuit takes a conductor, then they all use a common ground.
I grasp the general concept of this and would really like to give this a go, but just want to make sure that I have as much information as possible before I start so I'm not trying to figure it out on the fly....
I will say... take your time and MAKE SURE you understand what you are doing and how you are going to do it. It was a pretty cool project, but it was time consuming! Like I said previously, the spod isn't that expensive looking back, by I like my finished product better!