Ammeter wires

The red is a direct feed, only protected by the poor protection of the fuse link, from the battery. The black carries on through the ammeter and branches off to supply loads, then goes back through the bulkhead to the alternator. You need to at least bolt them together, AND I WOULD furthermore inspect the bulkhead terminals that those to use, as well as (at least) the dark blue "run" wire to the ignition. I also would install a large gauge, no 8, 6, etc, jumper wire from the alternator output to the starter relay "big stud" which amounts to "the battery." Put a large circuit breaker in that line, depending on the size of your alternator.