Stock thermostat is 82degC, I personally wouldn't run anything cooler.
MX83 radiator will be fine for a stock 1UZ, providing its clean and unblocked.
At about 10% blockage though, she'll start warming up.
Twin AU thermo's are also perfect, with a 95deg ON, 90deg OFF switch.
I've been running this setup in my MX73 for 2 years, and its been fine.
Even with the aircon on on a 35deg day its still fine.