Your sending unit does vary the amount of current sent to the gauge. Zero ohms or there abouts is empty & 30 ohms is full. There are many here who advise that you MUST put a resistor in line to the gas gauge. I am not an expert when it comes to electricity but when I converted my 55.1 to 12 volts I didn't put a resistor in the circuit & never had a problem. I may have just been lucky but I put over 100K on the truck after the conversion and the gas gauge worked OK the whole time. I can't recommend not putting a resistor in the circuit. I'm just passing on my personal experience.
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