i would say find the stock one, how much it can take, and use one around the same or slightly higher.

 

I might have missed it, but I would check the amperage rating of your alternator.I would run at least one run of 0 gauge even on the stock alternator just because its part of the Big 3 and you might as well do it up right the first time. That way if you get a bigger alternator in the future, you are prepared.