No headlights, fusible link at bulkhead melted…

I would DARN SURE check the alternator for a short!!!

I am thinking either the wiring has been hacked (modified) or you made a mistake, or maybe the link somehow made brief contact as you were wiggling stuff. You look at that diagram, here's how the headlights power works

Again, battery comes on the big RED to the fuse link, through the bulkhead connector, and to the ammeter. Through the ammeter, out the big BLACK, and a few inches away, the WELDED SPLICE. ONLY the headlight power comes off the welded splice, directly the the HL switch B1. The light switch has a breaker built in

Tail/ park/ instrument power comes from a fuse in the panel, which is fed through the welded splice to the fuse panel "hot" buss and the fuses that are hot at all times.