Trans Cooler + Gauges Help

[re34perGTT]

Hi all

Looking at upgrading my trans cooler on my r34 gtt. Just wondering if I can use any size cooler? Like I can't put one on that's too big ? Also will I need a new thermostat for a trans cooler upgrade and should I mount the sensor in the return line to the gearbox from the thermostat ?

Lastly this may sound stupid but are normal oil temp sensors and gauges the same as trans temp sensors and gauges ? Also when upgrading gauges like boost and oil temp can I just connect the new ones to the old wires or do I need to hook up new sensors and new power and ground wires ?

Any help would be greatly appreciated !