The fusible link is not the main concern, rather usually the plastic housing of the bulkhead connector melts. A little too much resistance (corrosion) plus upgraded alternator, generates heat (i^2 * R). Double the current and 4x the heat. Those wires may remain connected, but may begin touching other wires they shouldn't as the plastic melts. Too much current and resistance can also melt the ammeter connections and perhaps even damage the ammeter. There is a solution to keep your ammeter alive, yet protect it. Search for my post "Modernized Wiring" with my name (from google) to find a way with parallel diodes. Not for people who don't understand basic electricity. One gomer thought arguing with an engineer (me) there was smart. Another place to address corrosion is the welded "ALT" connection under-dash. Unwrap the fabric tape and you may find a green mess.
