The thermostat for the 4.7 engine is easy to get to. It is located on the lower part of the block. It is at the left side of the crank pulley (see picture).
On the 5.9 engine you will have to remove the belt and the belt tensioner to access the thermostat.
I have attached the instructions for both of the engines.
Remember to only work on the cooling system when the engine is cool.
Please let me know of any questions.
Images (Click to enlarge)
Friday, August 6th, 2021 AT 7:35 PM