Look at the left hand side of the motorbay, the thermostat housing is at the back of the engine, just beside the distributor.
You will need the gasket kit
https://www.burtonpower.com/thermostat-gasket-kit-ford-cvh-cv727k.html and the thermostat.
I suggest that you take few pictures of the thermostat housing before dismantling, as there is a lot of “traffic” in that area.