Sending units and gauge need to be in the same parameter. If you have a "Fox Body" fuel tank, you can use a 83-86 sending unit, which is 73 ohms (empty) and 10 ohms (full). I use Autometer gauges and the EFI sending units don't match to their gauges. I recently sent my gauge to AM to be checked/repaired. They offer a new replacement at 1/2 cost. Most of the EFI units are 22 ohms (empty) and 145 ohms (full). fyi