I'll be using the 'resistance' calibration method. I took both low and high resistance measurments before I installed the 22-gallon tank. Then after installing the tank and put in two gallons, I took a measurement. So I hope to be 'spot on' (or really, close enough) on the gauge.
65 Fastback, 351W, 5-speed, 4 wheel discs, 9" rear, R&C Front End.