You only need one for the fuel gauge sender. Years ago I went to Radio Shack and bought a big ceramic resistor, 60 Watt, its been working for 25 years now. I still use the stock amp gauges, even with A/C and electronic ignition, it hardly ever moves off center. I did notice last weekend it was charging 10-15 amps for a while, but it hasn't been driven for awhile and I had to crank to fill the carburetors. The resistor goes between the power source ( key switch ) and the fuel gauge. Keep it mounted out in the open to keep it cool, not bundled up a harness.
