Earthing

Through the flux capacitor. Unless you have a Cavalier, then there is no earthing, that's what makes them so reliable

Many years ago when you touched an automobiles that had recently been driven, sometimes you would be shocked by static electricity.

The tire manufactures started putting carbon in the tires to earth the cars and prevent shocks.

There were 2 methods of connecting metal frame to terminal of the battery,positive as well as negative

See that braided strap wotsit going from one terminal of the battery to the vehicle's chassis? OK? That's it.

Unless it's about the conductive dangly thingy that goes from the vehicle's bodywork and grazes the ground at intervals to discharge static? That could be it. It might need changing at intervals as is wears.

It's a floating earth. It's better than being mooned.

One 3/4" X 10' copper clad driven rod.

A $hit load (depending how far you want to travel) of #3 THHN bonded to the driven rod and vehicle frame.

I think it'll take two loads.