Before installing any sending unit, it's adviseable to see what the gas gauge reading is at various points of the potentiometer mounted on the sending unit. Where does it read full, half and empty. You will have to map these positions on a makeup cardboard template of your fuel tank being sure that the mounting flange sits at the correct angle. A slot cut in the cardboard will hold the side of the flange and tape will secure the pickup. Knowing the depth of your tank (profile), which you previously drew on the cardboard you can find the top, bottom and middle positions of the float and the gauges corresponding reading. You may have to bend the float arm or in some cases shorten or lengthen it to get the right reading. This is the only way to calibrate a gauge and don't be surprised if you find the float would hit the top or bottom of your tank if installed as is. Use temporary extending wires from the sending unit to the existing unit so you don't have to remove the gauge and make sure your template is on the same angle as the tank sitting in the car. An angle finder works fine for this.Once you're satisfied with the adjustments, install the unit. There are also digital boxes you can buy that act as an interface between any sender and any gauge for about $100. These require you to know the capacity of your tank and do simple adjustments as you add certain quantities of fuel. They work great and calculate ohmage output across the entire band from empy to full.
