Question about a old mad bypass repair

Fair enough, this I a fairly stock duster as far as wiring goes with no excessive electrical load, no AC, or power options , I believe a 55amp alternator, I guess what I was getting at is considering that the car came stock with fusible links is there anyway of knowing what a compatible ATO fuse would be? I guessed a 40 amp fuse was close to a 14 gauge fuesable link?