Fuel gauge issues

[Cleveland39]

I bought my '39 standard back in November and thought I had found the goose that laid the golden egg because the fuel gauge always showed full. Recently, fear of being stranded on the side of the road with an empty tank brought me out of my fantasy world.

I have tried measuring the resistance on the float. The older looking float was in the tank. The newer looking one came in the box 'o' stuff with the car. I am assuming (I know) the newer one came with the Dolphin gauges and was not installed due to the difference in the mounting plate. I tried connecting the wire to the newer float and when I turned the ignition on, the gauge still goes to full, regardless of the float position, just as it did with the old float. I don't have any instructions or diagrams for the Dolphin gauges, so I don't know what the resistance should be for different levels.

Can someone please steer me in the right direction before I replace the sending unit with a lit match?