The adapter is connected to the dash for the fuel gauges, I am swapping out to a digital dash. The digital dash has 1 wire, where the original has the adapter. Where do the wires go? Fuel tank and ground?
I have to think one wire goes to the sender and the other is a switched power such as an ignition 12V. You should be able to do some testing to see if you have power on the one wire and then see what resistance you would have on the other and then just to verify the sender wire, go to the sender or a connection point in the trunk and disconnect at that point and then whatever resistance you have before on the sender wire should now show an open or infinite resistance.