more wires....
i think that factory idea is screwy too... my battery is grounded to a bolt on the framerail, from that same bolt, i have a fat wire running to the engine block, and one from the bolt on the frame to the body..
it would be a good idea to replace the wires just to do it.... corrosion can hide in the wires under the insulation, and if the wires are old, its jsut good to replace them