From ETB's website
ETB manufactures 2 types of fuel gauges.
The first type is matched to our standard, 6-hole, top-mount float-arm sensor. This sensor is calibrated to provide an electrical resistance of 260 Ohms at empty and 20 Ohms at full. This calibration range is similar to early Smith's type fuel level senders, as well as some Ford fuel senders (most commonly 1982-1986 Ford Sierra hatchback / saloon).
The best way to check whether your existing fuel level sender will work with an ETB fuel gauge is to measure the resistance range of the sender unit. To do this, you need to disconnect any wires connected to the sender unit and remove the sender from the fuel tank (taking great care if there is any fuel left in the tank). Using a multimeter that can measure resistance in Ohms (Ω), connect one probe to earth and the other to the connector on the fuel sender and note the resistance reading with the float at empty (lowest position) and at full (highest position).
If the reading is approximately 260 Ohms at empty and 20 Ohms at full, it will work reasonably well with an ETB fuel gauge.
BUT!!!
These sensors were not designed to work with the modern ETB air-core movements, but with old bi-metallic strip gauge movements. Therefore, although empty and full will be correctly indicated on the gauge, mid-range indication will read incorrectly. This is because ETB gauges expect a relatively linear change in resistance as fuel level changes, whereas the older Smith's type / Ford type are not linear - this basically means that fuel will appear to decrease very rapidly from reading full for the first two-thirds of gauge pointer movement and then slow considerably when the pointer nears empty.
The second type of ETB Fuel gauge has a range of 10 Ohms at empty to 180 Ohms at full. This type will match certain VDO lever-arm type fuel senders.
Hope this helps........