Alternator wiring question

Hello all.

I've got a Denso Toyota alternator that's rated at 100 amps (might be 90). I've done a little research and I should be running 4 gauge battery cable to a 100 amp fuse then to the battery.
Is this right? I somehow doubt the factory ran a 4 gauge wire. If it doesn't need to be 4 gauge..what gauge should I use?

Thanks in advance!