revisit the fuel gauge and sending unit issue

If you build your own voltage regulator, instead of using a fixed 7805, use a LM317 or LM350T. They are adjustable regulators that use the same TO-220 package. The data sheets can be found on Google along with circuit designs. Only a few resistors are required for the adjustment circuit. I had one in a car and it was calibrated to read correct at empty. Beechcraft has used adjustable power supplies in some of their airplanes and they calibrate them to read correct at empty. I personally like to have the gauge more accurate at empty to show if you have too little gas, because the only time you can have too much gas is if you're on fire.