Quote:

The most electrically conductive element is silver, followed by copper and gold. Silver also has the highest thermal conductivity of any element and the highest light reflectance. Although it is the best conductor, copper and gold are used more often in electrical applications because copper is less expensive and gold has a much higher corrosion resistance.




http://chemistry.about.com/od/elements/f/What-Is-The-Most-Conductive-Element.htm


I run my cars much like Monty suggest. I ground the frame and run a dedicated ground circuit for sensitive electronic/ignition.

One thing to watch for on cars is ground looping. It may create static and noise.