Is there some reason not to use an old school potentiometer, and dial in whatever resistance is needed to handle the load of the gauge? Simply connect the ends of the resistor to power and ground, and dial up the movable contact to get whatever voltage makes the gauge work most accurately. Lots of potentiometers have a lock nut to anchor the shaft down once the proper voltage is achieved on the wiper contact.
Jerry
If I am reading this correctly (which I am very unsure of...), you are suggesting using a potentiometer like an old rheostat to drop the voltage to an "ideal" value for the load that the gauge puts on it. The difficulty with that is the load from the gauge varies by about 50% depending on how much fuel you have. So putting any kind of a static voltage divider in the circuit is problematic.
If I am not reading your suggestion properly, please correct me.
