The factory dash is plastic though.
All of my autometer guages have thee basic wires in common. Red (12v fused protected power), Black (ground), and White (12v for lights). With these three you get power running and in case of the voltmeter, it is completely hooked up. You need to make sure the ground is secure to a metal surface that is actually grounded to the battery. The red wire you should be able to tap into any ignition activated 12v wire but make sure it isn't a wire that will power a lot of accessories. It will cause the wire to get hot if too many amps are drawn. The white one can hook into the factory lead to the dash lights. The most common problem is the bad ground. You need to make sure you have the wire touching a metal surface and not just sitting on a painted surface. I like to use the areas where the dash frame bolt to the car for my grounds. That way you aren't creating any new holes with screws or bolts.
As for each individual guage, the remaining wires just hook up to the corresponding sending unit.
When you turn the power on the gauges should cycle, even with out the sending units hooked up.
