Ground is usually the voltage level all other parts of the circuit are measured or referenced from.
That stated it is possible to have different circuit paths connected to the same GND pin. However, the maximum current for a single pin is 200 mA (or 0.2 A) and you shouldn't try routing more than 400 mA total through the ground return on most Arduino boards. Within these limits you can connect any combination of gagues and resistors to the on-board ground you want.
Of course if you wire the resistors directly to the ground of the power supply (in this case the wire that goes to the negative on your car battery) you don't have to worry about the current going through the gauge. You'd just have to use opto-isolators to get the signals from the gauges instead of connecting them directly to the Arduino.