I suggest that the first thing that you do is make a diagram of what you have. It sounds like the wiring on this truck has been modified from the original (based on the fact that it has electronic ignition and you use a key to start it) The diagram can be very helpful if something goes wrong and you have to retrace your steps. Also, I find that making a drawing helps me understand what going on.
You don't have to draw everything - concentrate on the ignition and charging circuits. Draw the wires between the starter, ignition switch, electronic ignition, regulator, main feed to the lighting switch (connections at the end closest the firewall) and the horn relay. Record the color of each wire.
The other posters are correct in that there should only be one wire (a nice fat 10 gauge) from the bat terminal on the starter to the + on the ammeter. The other post on the ammeter should connect to the bat post on the ignition switch, lighting switch and the B terminal on the regulator. In my case, there are only two wires on the - side of the ammeter; one to the lighting switch and one to the ignition switch. There is a strip with three terminals on the back of the lighting switch so the horn relay B and regulator B wire connect there (works the same as connecting them all to the ammeter)
The wiring on these old trucks can vary greatly as previous owners have made upgrades and repairs. Another good reason to make a diagram and take stock of what you have first.
