Non Mopar Battery Isolator question

The original wire from the alternator in this truck was only about 1' long. It attached to a factory tap in the cable from the POS battery terminal and the starter. With that being said, what size wire should I use to replace it with?
Here is what I have on hand:
1/0 gauge wire
9 gauge wire
5 gauge wire
(The 9 and 5 gauge wire is from a stereo amplifier install kit I scored at a thrift store for 3 bucks. I just wanted the wire.)
thanks