That circuit will be carrying the full output of the alternator after cranking the engine, so if you choose to fuse the circuit, go about 10% over the max the alternator can produce. That will protect the wiring harness from a short, but it won't blow a fuse if you have an extended cranking session (flooded, etc.) and the alternator goes to full output for a while.
You could also put a 10 gauge fusible link in the circuit instead of a fuse.
Jerry
