These(60-66) have no protection before the fusebox, what has likely burnt up is the ammeter shunt wiring, usually(& melting a nearby wire also) near the inst panel. These two black w/white tracer wires run from the horn relay to the inst panel, the other runs from the panel tot he starter relay. Pull your inst panel & check(untape & inspect)the harness behind it. The big pink wire from the ign. switch feeds the fusebox accessory side IIRC. You could also pull the fusebox & see if something is up there.
