97 deville 4.6 northstar, where is the thermostat?

Just follow your UPPER radiator hose FROM the top of the radiator (passenger side), across the front of the engine compartment.
It will end at a (black) metal hose connection. Remove this connection (2- 10mm bolts) and there you will find the Thermostat.

The thermostat is not located on the upper radiator hose. The thermostat is located on the lower radiator hose. To access this, you must take out the air cleaner box. You will see where the lower radiator hose meets the block. It is 2 bolts to take the housing off. Good Luck.

Cadi197 is correct. Lower hose.