alternator upgrade

[chevyhed53]

I'm getting ready to add some accessories to my barebones '56--nothing dramatic, some tunes, upgraded lighting--and I'm swapping my old 55 amp alternator for a 100 amp unit. The wire from the alternator to the starter is no bigger than 10 gauge, and I've been told I need to run a larger wire with a bigger alternator. I've got a roll of some very nice 4 gauge wire sitting on a shelf. Is that too big? Is it possible for main power wire to be too big??
Thanks!