usually to save costs they don't, and yes the amperage of the alternator is a determining factor, the mazda 3 charging system will never have enough power to over power 0 gauge wire it simply just cannot make that much power a 150-175 amp fuse should be just fine for your needs, the fuse between the battery and the alternator is also not a 100% necessity, its a safe guard. the alternator on the 2.0 and 2.5 non skyactivs are 100 amps and underI used 0 gauge wire. Doesn't the amperage of the stock alternator determine the size of the fuse? So I'm still unclear on the answer.
Also, do I really need one? How come big 3 kits don't come with fuse holders?