As to your ammeter, see,
http://www.moyermarineforum.com/foru...8&postcount=24
In general, if your ammeter is the standard automotive round 2-1/16 ammeter, then it probably has an internal shunt, and is wired in series with the load using biggish wires, like #2, #4, #6, #8. These meters usually are zero center scale, so they can read positive or negative, and look like the below image.
If the meter has an external shunt, the two wires should be small, like #14 or #16, or even smaller, since the shunt output to the meter is only a few milliamps at a few millivolts. And you can follow these two small gauge wires from the meter back to the shunt, which will have two large wires from the load. In addition, it is customary (even in the 60s) to mark meters that use shunts, either on the back or on the face, with the shunt ratio (100A = 50mV).