Help adding a trans temp gauge

[Chevy1TonFun]

I have been going back and forth on whether or not to go with Autometer gauges or buy the white faced stock gauges. Here is my first question. Can I add another stock temp gauge in place of say my vacuum gauge and have it read the trans instead of the engine temp? Next question is where should I install the sending unit? The three ideas that I have come up with are 1. install the sending unit instead of the drain plug on the pan, 2. weld a bong on the pan, or 3. install a tee at the cooler. Thank in advance for the input.