I dont recommend a Tee fitting for any temp gauges. Because both senders are stuck in a tee, and not in the real-time flow of fluid, the gauges tend to react with radiant temp changes (because they are not succepted to the flow of coolant, but rather sitting in an alcove of coolant).
I would use the stock location for the new gauge (it is the best location) and even buy an aftermarket t-stat housing for the stocker (if the stat sticks closed, that gauge wont tell you, but it sucks anyhow). One can use a chrome FRPP t-stat housing (under 30 bucks) but they can leak if some chrome is not scraped off. Or AZ/DAP sell cast housings for 10 bucks that rust. I run the latter.
Good luck.