What I would do first is find the temp sending unit on the engine. It will be the single wire sending unit, not the two wire sending unit. Take the wire off the sending unit, and then with the key in run, engine off, observe the temp gauge. It should have swung full scale one direction or the other. Then with the key still in run, take a jumper wire or something and ground the wire that went to the sending unit. When you do this, the temp gauge should swing full scale the opposite direction. If it passes this test, the guage and the wiring to the gauge are good, the sending unit is bad.
You can also do this same test with the fuel tank sender if you can get to the wiring and figure out which wire is the sending unit wire. Many of the Ford senders use a yellow/white wire.