Finally something I can contribute to in a useful manner!
I've put invertors in two of my trucks, and will be putting one in one of my cruisers sooner or later (I noticed you mentioned the possibility of installing an A/C outlet), so here's my two cents.
1) Buy a good one. The 450 watt invertor for $28 at Sams Club will not give you the same power as the 450 watt $50-$60 (I forget) Husky invertor at Home Depot.
2) After you buy an invertor, use it before you install it. A lot of them have a constant fan. Doesn't draw enough power to be a worry, but the noise drove me crazy. That's how I ended up with the Husky from the depot, it's fan only works when you switch it on. I think I bought and returned 3 before I found that one.
3) Bigger is better, but remember you need to put a fuse in that can handle the draw. If I remember correctly, the rule is watts/9. That means a 450 watt invertor needs a 50 amp fuse. My local Napa didn't have one, in fact they looked at me like I was a moron for even requesting it. Autozone did, and also had a waterproof holder, so it worked out, but had to drive twice as far to get it, and of course I always just jump right in, so I had the truck all torn apart, had to borrow the Subaru, etc.... Anyway, imo 450 watts in the smallest invertor that will be useful enough to justify the install work. Plenty of power to run an airpump, blenders in the desert, etc...
4) Bigger is better for wire choice as well. I think I used 8g last time, and I ran the power and ground through the frame rails under the truck, and then in through a grommet in the back wall (it was a 4 door tacoma). I wrapped them in some hard split loom. Worked out really clean, and never had to worry about them rubbing, etc...
5) You could easily run the wires under the carpet, but 2 8g wires is a pretty thick bundle, think carefully about where you place it.
6) As mentioned before, if you use the side poles that are rated to 25amps, you can only safely use a 225 watt invertor. That will charge a laptop, but it may not spin a blender. Once you get used to having some outlets in your truck, you make up excuses to use them. On a good note, I wouldn't worry about running the power and ground to the main poles (the install instructions on my last one suggested running the ground directly back to the battery). You won't typically be doing anything else when you're using the invertor, so the draw on your battery won't be too huge.
Hope that helps.
-Matt
