It might make a tiny difference, but at 80 amps the voltage isn't going to drop that much in that short of wire either way. Now if it was a 320 amp alt. then you would be looking at 4x the voltage drop in the same length of wire, which may come up to be a more noticable number.
Edit: Just for piece of mind I calculated it out. In a 4 foot run of 4 gauge copper wire with 80 amps of current the voltage will drop .07952V, and that is if he removes the original wire and only uses 4 gauge. With a 4 ft run of 0 gauge copper wire with 80 amps of current the voltage will drop .031456V.