I bench tested everything on an Ebody rallye dash before selling it using a car battery and a 5 volt power supply.

Speedometer: spare speedo cable and drill
Clock: + / - connections using the battery
OIL, FUEL, TEMP: + / - connections using the 5v power supply, just looking for movement not accuracy.
ALT: I put 2 road lamps in series with the ammeter and battery, the needle deflected to "D" (as pictured).