The thread for all the temp sensors I'm aware of is a 1/2" pipe thread. Putting the temp sensor into the block might give a lower temp indication by a few degrees than the below-the thermostat location, but not much difference, IMHO. The coolant is the hottest right before it enters the upper radiator hose.
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!