Yup, that's my little one.
I had a brief minute to snap open the back doors to the cabinet and look at setup that is left. From what I can see, it looks like each player had his own setup, which not only consisted of all three boards you got, but also a standard power supply, a transformer,and a couple other wires. Check the pictures:
This is what the compartment looked like in the back of player 2 side. You can see, there's the transformer which sends a couple wires over to the power supply, as well as a 5-pin molex bundle which connects to the smaller board (sound I think). At any rate, only four of the five pins are used.
Jeez, I marked some of the wires, but didn't document any pictures to show how they were setup. At the time, I was thinking if the XBOX thing didn't work, I was just gonna put it all back together.
As you can see, Player 1 side had the same 5-pin molex pinout which was removed from the seperate smaller board. Look on the smaller boards you got. Whichever one had the 5-pin prongs on it, is the one that is supposed to have this power.
So in theory, you should have received from Jered:
1. There should be a seperate set of wires which connect player one to player two for competitions.
2. You should have the MAIN harness, which connects to the MAIN pcb pins and will have some ground, -5, +5, and +12V wires that go to the power supply.
3. Also in this main harness should be a bundle of wires which head up towards the monitor. Will probably have a small 3 wire molex and a small 4 wire molex. These look standard, so you will recognize them.
4. Also in the main harness will be wires which go up to buttons and pedals.
5. And if memory serves me right, there were some wires which came from the main harness and attached to a set of pins on the steering boards (they might be 2 red wires or something.) Then, some other wires from the steering board went up to the actual pots on the wheel.
6. There is probably some sound wires which come from the main harness and attach to the sound board which is then wired to transformer.
Like I said, it was a while ago, so my memory is a bit fuzzy on the wiring. I've got so many wires all over the place in there now, that it is very hard to see what I'm doing. Actually, if you're lucky, I think I tried to tag what each section of wires went to on atleast one of the harness setups. Hopefully you received it all with those still intact. I'll wait to see what you find out.