Fusing an alternator is almost a waste of effort. The stator is self-limiting as far as maximum current output goes, and about the only way to make an alternator short out is to connect a battery or a set of jumper cables backwards. If you choose to fuse the alternator, use a fuse that will carry its full output plus 10%. A 55 amp alternator would need approximately a 60 amp fuse, etc. 70 amp alternator- - - -80 amp fuse. Remember- - - -fuses protect the wire, not the end item in the circuit. A fuse will not prevent a component from shorting out or wearing out; it only keeps a wire from burning.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!