Cusser
+1y
That air duct/hose are to bring in air (air cooler than that under the hood) to your air filter/carburetor. I've already sold mine, get a used one or duct-tape yours.
Fuel gauge issues are primarily due to sending units needing replaced, or cleaned and the contact arm bent. This can be accessed by tilting the truck bed, I've posted details and photos how I do this on mine, do a Search.
For coolant temperature, first make sure that the wire is still attached to the sending unit, underneath the thermostat outlet pipe.