For my home brew FWC, I am using the following:
Stant 14077 170 degree THERMOSTAT $10.88 at Advance Auto Parts
Stant 27286 thermostat gasket seal ring $1.99 at Advance Auto Parts
For closed cooling, the 170 deg t-stat above should be ideal. It also physically fits perfectly in the housing.
The "aluminum sleeve" I mentioned above needs to be 1.9" diameter to fit over the thermostat, at least I THINK it fits over the thermostat as best as I can tell from the instructions. I still would like the inner and outer and length dimensions of it.
Also, please take pictures of the goodies in the kit BEFORE it is intstalled, thanks!