You should see the cables I'm making this weekend for the battery to starter, starter to Alternator, and transmission to battery I believe its arround 3/0 AWG
The cable is from a E30 BMW with boot mounted battery
Just got the M10 cable lugs today for the alternator & starter motor + terminals and for the transmission ground
going to link the battery directly to the transmission ground then from the trans ground to the body ground in 4 AWG cable
Total overkill but I've had this cable lying arround from when I was going to boot mount my battery but couldnt be bothered.
The cable from the battery to the starter is just the starter to engine bay remote battery terminal cable, the rest I'm making out of the battery to remote battery terminal.