Just a thought, I have a powerful ICE system installed in my00, so i'm thinking of 'upgrading' the earth cables under the bonnet. What's the best way?

I'm thinking of using some 4AWG cable from the earth on the battery straight to the chassis, to back up the crappy ,thin existing cable as i dont think this is good enough, also is it worth running some 4AWG straight to the alternator body. I do have a split charge system wired with a mix of 4 AWG and 0 AWG for earthing points.