can earth on any part of the car as long as its not a positive
best places would be chasis , stut mounts , any thick metal
make sure u sand grind the paint off for best surface contact
main ones to upgrade would be battery to body , battery to engine , engine to body
I read something today that said to link up a stronger earth from alternator to thermostat earthing point and the battery to improve general earthing, thought that was pretty nifty and made sense... can see the volt go up and down on my inside voltage gauge. So going to try that see if it stabalises it a bit, if it can really be affected.