Burned bulk head connection

Hi, the ballast resistor is modified to let 12V going through (got it from halifaxhops), other than that everything should be stock. Removed all the performance stuff, which the privous owner added. I wanna keep it stock, besides the electronic ignition. Alternator should be 69, will post a picture tomorrow. Just checked the wires inside the firewall again. So far they seem to be in great shape. If I just replace the black alternator wire, would it make sense to add a fuse or other safety feature in it, just in case the wire gets too hot?