you can use any temp t-stat . depending on your setup and needs.
I use a 75degree, it stays really cools, but if you drive in the winter/cold weather you wont have much heat. the closer you are to 92(stock) the better your fuel economy will be.
theres 75, 81, 88 and 92 degree t-stats available.
up to you really.
change your water pump while your at it!!