Ford's Orange 16ga fusible links are rated for 22amps, (+/-3amps)
So there would need to be one for cab/ignition switch
And one for alternator/charging system
I can see these being linked together, not a great idea, but most of the alternator's amps go to ignition switch not to the battery, so that one fusible link wouldn't see too many amps, but then alternator is not protected by a fuse, a short in the cab wiring would smoke the alternator, fuses and fusible links are there to isolate and protect 12v wires and devices
Headlights also need a fusible link at starter relay?
I just can't see running the whole vehicle on one fusible link, you could, just shouldn't, and they cost $4-$7 so...............it ain't the cost, lol