[Michael C Henry]

The actual ignition switch doesn't need to be grounded. It could be located in plastic and there would be no difference. You move it it just makes or breaks electrical connections. Any thing that operates or moves by electricity needs to be grounded gauges, starters, solinoids,If the engine is grounded properly it is the groud for temp sending unit ,strter,spark plugs etc.The fuel tank needs to be grounded for spark suppersion and the fuel quantity sending unit that grounds to the tank. The starter solinoid is a electro magnet and needs to be have the housing grounded to operate the magnet thhat connects the heavey switch. The Dash needs to be grounded for the gauges and lites.On a fiberglass car, ground wires need to go to almost all componets . Most componets were intended for 12V neg ground systems on conventional metal cars . Most of the time the metal car was the ground syteem but some manufactures still ran an extra ground wires just to be certain.Copper cables carry more curant and have less resistance than steel frames.The grounds are all interconnected to form a system connected back to the battery. Do not forget the ground path back to the battery for the alternater usually through the engine.