The thermostat designed for use with that housing is obsolete and no longer in production. Simply using the housing without the correct thermostat creates a constant leak of hot coolant back to the water pump inlet, possibly compromising cooling when the engine needs it most- - - -heavy load operation at full throttle.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!