Fuse the circuit to the maximum output of the alternator plus 10%. For instance- - - - a 55 amp alternator would need about a 60 amp fuse, etc. After a long cranking session to clear a flood situation, etc., the alternator will go to full output for a short time to replenish the battery drain. If the fuse isn't capable of handling full output of the alternator the fuse will blow. It will still burn out and protect the wire harness in a dead-short situation. Use at least 10 gauge wire from the alternator to the ammeter and the same from the ammeter to the battery cable terminal. 8 gauge is better if you can find it.
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!