You've got the basic idea. Cut a strip of the clamp that's solid, about 2" long or a little more, and bend it into a "U" shape with tabs bent at right angles to the main loop. It will resemble the "Ohms" symbol used on wiring diagrams. Drill holes in the tabs to fit over the ammeter terminals. Install the shunt onto the terminals, then connect the wiring as usual. All the connections EXCEPT the wire going to the starter cable connection get attached to the downstream side of the ammeter. That way, all the current going in and out of the battery except the starter current passes through the ammeter and/or the shunt. The shunt prevents the ammeter from deflecting full scale during heavy current situations like just after starting, while still allowing enough current to take the original path to indicate a charge/discharge situation. It's a simple, inexpensive fix that protects the original ammeter from overloads.
Jerry
