I swear this damn thing is like Bigfoot....... either you've seen it or you haven't. The housing is non traditional and the screws are buried out of sight so this internet is bustling with people TRYING to explain it, but no pictures to be found...... because it is hard to see anything!
I made an attempt to take a few pics so I hope these work out for someno looking to replace their thermostat.
(1) Make sure to remove the fan shroud from the radiator, it diesn't havr to be removed from the truck, just get it to where it can move around some.
(2) Use a magnetic telescoping tool to remove and install the screws back into the thermostat housing/block. if you don't you WILL drop them in places you can't see.
(3) There is buildup and corrosion behind your thermostat in the block so take the extra few minutes to re-attach the housing without the thermostat and blow the line clean with a free running flush.
Look down to the circle on bottom