Tee fittings will give a false (low) reading, since the sensor will be out of the flow of coolant and the extension of the fitting will act like an insulator. The driver's side rear area of the head beside the valve cover flange should have enough thickness to drill and tap for a 3/8" NPT thread. Use pipe dope or brush-on gasket sealer on the sensor threads.
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!