back to the trans temp monitoring
I believe that the best place for the sender is in the pan.
Though the cooler line going out (the forward line) is also a good place as long as it's as close to the trans as possible.
I am not a Torqueflite authority, but I am pretty sure that the outlet line fluid was in the pan, just up through the pump and part of the valve body (the regulator)- and not in any other part of the trans before it's been to the cooler, What happens to the fluid after the cooler (the rear line), I'm not sure about. I don't have my FSM with the cool transmission diagrams handy.
Basically, with no extra load, my needle stays on 140, which is the stop, at all times unless I'm in traffic where I've seen it go to 160-80, but cool right down as soon as you move.
The pan location seems like the way to go since it doubles as a drain plug too.