The best place to install the sending unit will be in the tranny pan. Here's a couple of
pics from my recent tranny pan install. The next best place would be in a section of the rubber line leading out from the tranny and before it enters the bottom of the radiator. The tricky part is getting a good ground so that the gauge works properly. Not an issue when mounting in the pan.
For gauge location, I'm not sure an A-pillar pod is available for the 2005's. You could mount one in the location just over the transmission tunnel like I originally did in this
photo.
You can pick up an Autometer gauage from Summit Racing, it comes with the sending unit.
Have fun with the mod.