A lot of self-appointed "experts" spread misinformation about an ammeter being a dangerous fire hazard. I'm amazed that any of these old trucks survived long enough for us to get interested in restoring them, since millions of pre-1960's vehicles should have gone up in flames shortly after they rolled off the factory assembly lines! An ammeter is probably the most rugged instrument on the dashboard. Even if a high-capacity alternator is substituted for the generator, a very simple home-brewed shunt will keep the ammeter from going full scale while the battery is recovering from the high current demand of the starter.
Yes, one wire at the ammeter needs to go to the battery cable terminal at the starter. All other connections, including the charging lead from the alternator or voltage regulator attach to the other side. When the circuit is connected that way, the ammeter will indicate both charge and discharge current. If you connect the charging system directly to the battery without the ammeter in the circuit, the ammeter will only show "discharge" as current is supplied to the ignition switch, headlights, accessories, etc.
Jerry
