The sending unit needs to be the correct resistance for the gauge that it's connected to. You may be able to use the existing sending unit if it's functioning properly. Find out what its nominal resistance is, and then look for a gauge that uses a sending unit with the same resistance. Most aftermarket gauges will specify the resistance, in ohms, of the proper sending unit.
Since money is tight, perhaps what you should consider is finding a working combination. So long as the gauge is 12 volts and will fit in the dash, and the sending unit has enough travel to at least somewhat accurately tell you when the tank is empty (because that's all that really matters, right?), you should be able to use almost any sending unit/gauge combination that meets those requirements.
Last edited by baldeagle; 07/27/2009 2:39 AM.
