I have been reading the forum for almost a year but I haven't posted too much. In that time I have learned quite a lot. I am very appreciative of those that have shared their knowledge. In return I thought I would post my recent project.
In anticipation of picking up a new camper from ATC at the end of May, I wanted to install a second battery to run a fridge, lights, furnace and accessories. I decided to mount the battery in the engine compartment for weight distribution reasons and ease of battery maintenance. A plus is that the battery is still there to backup the primary battery when the camper is off the truck. I learned how to do this from other posters on this and the Tacoma World forum. When the recent IBS group buy popped up (another benefit of the forum) I decided to participate and today I finished my installation.
I bought a Sears Diehard Platinum 2 which I also got on sale with an additional discount using a code (Sears2012) I also learned about on here! I mounted the battery in the engine bay on the passenger side where there was room and a convenient set of unused factory studs to mount a plate to hold the battery. I found two factory bolt hole locations to mount the relays near the factory battery. I routed the controller wires through a factory grommet in the firewall. I removed the coin tray on the right side of the steering wheel (which I didn't use anyway) and mounted the controller in the space left after removing the tray. It is visible and easily accessible but out of the way. There was room to mount my garage door opener there too. I am pleased with how it all turned out.
Here's a few pics: