The thermostat starts to open at 160 deg F., then fully open about 180 deg F.
The safety Switch is calibrated to shut the engine down at 220 deg F. on the 2008 and older models. 2009 and newer utilize different systems. I assume you are requesting info for the 2008 and older machines.
We do not offer a mechanical gauge. If you so desire to change it, then you would need to source it locally.
As additional information, you can go to www.toro.com
and download a free service manual if you desire. The manuals have all the information in them!
The Toro Company