[dsraven]

what I have done in the past is bring a decent sized (large enough for the max amp draw on the circuit) set of power and ground wires up to a bus bar or insulated stud behind the dash. then run wire to the first gage light and then chain the power and ground circuits for the rest of the lights, because you wouldn't notice a slightly dimmer light due to draw on a single feed wire. then run power and ground wires to each gage for the actual gage function so they see equal voltage at each gage.
electromechanical gauges use a dual electromagnet system to pull the gauge needle one way or the other. one magnet is constant magnetism and the other magnet is variable by how much power or ground the electromagnet sees through the gage sending unit. the gage needle sits between these two magnets. so if the sending unit sees less of a circuit then the variable electromagnet in the gauge is correspondingly less strong compared to the constant strength magnet and the needle of the gauge is drawn towards the stronger magnet.
make sense why you would want full voltage to each actual gauge circuit, not shared voltage with lights, other gauges, stereos, heaters etc?