Bench testing dash clusters ??

Of course. You want to check the gauges for some sort of accuracy, or just lights, or what?

http://www.forabodiesonly.com/mopar/showthread.php?t=179517

http://www.forabodiesonly.com/mopar/showthread.php?p=1970997882

With all the parts you probably have kickin' around you could probably just use a tank sender, and use an ohmeter beforehand to set it for the various test resistances. In fact you could mount it, and mark the arm for proper positions to test MT, 1/2 and full. That sender / resistor can be used to test oil and temp as well.

Of course you need a source of power. Best would be a 13.8--14V regulated bench power supply. You can buy them, in various forms, pretty cheap.