Got some time to do some errands yesterday and today. So getting back to the aux tank. There are probably a million different ways on getting this done. Years have passed since the install was done by mud members who are listed in the FAQ.
Fast forward to 3/2015. Dead horse topic of rivnuts or rivet nuts (same thing).
The tank came with the M10 bolts but had a thread of 1.25. If you search for rivnuts in a M10 to accommodate 1.25 thread, you won't find it.
After going to McMaster, grainger and fastenal, the only Rivnut to accommodate a M10 bolt is with thread 1.5.
Now, the bolt that Toyota used and came with my aux tank, had a washer and crush washer on it. From what I have researched (which wasn't too much) was on why did the Toyota M10 bolt came this way.
One was measured with 40mm and the other was 30mm
I was able to recreate this setup by going to Home Depot and finding the bolts / washer / crush washer. Spent $12 to get the M10 bolt with 1.5 threading. Now I have to go back to Grainger and make sure they will fit. The pack of 25 rivnuts are $42 from Grainger.
I was able to also get the project box and a 9 pin male/female connectors from RadioShack. Another $10 since I want the chip to be protected. I will drill a hole and place a rubber grommet to allow the wires to exit the project box. Once I see someone with a drill press (or I'll drill it myself at home)