RE: Trans Temp Gauge
I would install the sender as close to the trans as possible. I think with a gauge like this, you want to measure the fluid temp as soon as it comes out of the tranny. If you instal the sender up near the radiator, or cooler, I'd be willing to guess that your reading could be as far off as 15 to 20 degrees, due to the fluid running through the length of the metal line, and loosing it's heat along the way.
Anyone else want to chime in?