could be done, but would have to be real careful with the wiring powered and the cluster loose .... and yes, need to put a temporary ground from the cluster to the dash ... could maybe check using the ign sw easier, the pink wire Jon mentions should go from the ign sw to the power terminal on the gauge - with the key on you should read a voltage from that pink wire to ground, or [with the key off] there should be continuity [ohms] from there to the green wire at the engine [using any piece of wire to reach]
Bill
