Have you checked for voltage to the fuel level and temp sensors?
The temp sensor should be easy enough to find. The fuel level temp sensor [should] be (I have no way to confirm this from here) yellow with a white stripe. See if you have power.
The signal wires for both, should be right around 5 volts.
The signal wire(s) for the ECT should be LG/R and GY/R. One feeds the gauge and the other the EEC. You will have to confirm these wire colors.
The wire feeding your fuel level sender should be Yellow with a White stripe (YE/WH).
If you have power to both senders then test the gauges next. If not, check fuses, wiring, and grounds.
All of this would be tested with the ignition in the [On] position.