I'd like to squash the 2 gauge before this gets out of hand. I don't know how many times I've heard "Dude you need at least 2/0 gauge to start your motorcycle/Honda/lawn mower", etc.) Someone's been buying into the car audio hype about needing massive wire size for no logical reason (well, profit is logical I guess).

2 gauge is massive overkill. It won't hurt anything, but it's overkill. It sucks to have to run it and hide it in a car, too..

4 gauge is more than fine, it's rated 135-150 amps continuous at 15 feet. I don't think you'll have a problem. Your current can be much higher than that for short duration also, it's all about heat dissipated from wire resistance. You don't need to source a constant 150 amps, do you? I know a lot of the kits come with 2 gauge, which is fine. Be sure you don't use car audio wire though, that's garbage wire. Use decent automotive grade wire (just like your stock battery cables are made of) and make sure you put a fuse or breaker on the battery end of the wire. Burning the car to the ground isn't something you want to do I'd imagine.

Just because someone sells a 2 gauge kit, doesn't mean you need it. Starting a high compression V8 from the back end of a long chassis with the headlights on and the stereo cranked, maybe.