Is that 2-1/16th" gauge size or is it a rectangular screen?

rectangular mounted to piller,

the newer monitors are reading factory sensors over the can data bus through obd 2, your truck has very limited info via obd2.

I'm getting conflicting opinions on placement of temp sensor in 47re tranny pan............some say the readings will be much cooler here.
was going to add a drain plug and install temp sensor through it .............I've read where the fluid in the pan can be as much as 15* cooler
than say the "oil cooler line".

The sender comes with a bung to weld in place. Once welded, I drilled thru into the pan and now its a drain plug also.

As for if one is hotter then the other, probably so before the cooler. Lets say its 20 degrees cooler then the pan, so running around with no load and with load, you'll notice if it gets hotter then normal

But my point is, would using the sensor in the tranny pan be good enough to get an accurate temperature reading?

Accurate temp of the fluid in the pan. If you’re within 15* of your upper threshold you know there’s an issue. Also no matter what the gauge says, if it’s almost always at xxx degrees and hauling the boat one day it’s xxx+ 20* you know there’s an issue starting to arise.

I guess using the words "good enough" for an accurate temp reading in the transmission is a loose term...........finding out the pan might be the worst for placement of temp sensor.

Hmmmm...Is there such a thing?........ a 47RE Transmission cooler line with test port built into it?

it can be made easy enough, I don’t see a need to do it that way, but whatever you prefer for your truck is the way you should have it installed.