will a 68 dart amp gauge handle 78 amp alt?

The large wire from the alt goes through the bulkhead connector to one side of the amp meter, the other side of the amp meter goes out through the bulkhead connector to the fusible link and then finally to the starter relay.

The easiest solution is to run a lead (8 guage) from the alternator to the bulkhead connector side of the fusible link, and then run another wire from the same side of the fusible link through a hole in the firewall to both terminals of the amp meter,do not disconnect any of the existing wires from the amp meter. This will disable the amp meter and eliminate all of the current form going through the bulkhead connectors. You will also want to add a volt meter to keep an eye on the charging system status.