I have the single t-stat and loaded up a little in the hills of southern Ohio with A/C on and 90-95 degrees out, I didn't need to turn off the air conditioner. That is with an OEM which I believe is 195. It didn't really offer to get much warmer than typical unladen.
An internally plugged...
I replaced the ones in the rear also - 4x6 maybe? They're hard to get to on account of the need to remove the ceiling trim and loosen the pillar plastic but I got it done and no clips broke. The speaker location is fine for metal heads but others might complain.
If I remember right, I left the one above alone and just replaced the lower.
I think mine are Sony
I didn't have to fish any wires but I bought from Crutchfield so I would have gotten an installation kit if it was needed.
I believe you would stay cleaner if mounted forward of your rear axle. Is there enough airflow between the frame and bedside on the passenger side?
Sort of opposite the fuel fill side
Passenger side of differential casting. 3/8" short extension will plug right into the square hole. Might need to clean it out the hole with a pick or screwdriver to get a good bite.
if you refill, use a synthetic with friction modifiers or get the additive for posi-rear.
Probably a good...