I've got some factory diagrams stashed away somewhere. The circuit is different for applications with an ammeter than the ones with an idiot light. The ammeter-equipped circuit needs a resistor in it somewhere, don't remember exactly where, to keep the engine from continuing to run when the key is turned off. Been there, done that! I'll try to post a diagram when I get back to the farm in a couple of days, if someone hasn't helped out by then.
Here's a circuit that should work. I don't know if your system has an indicator light or an ammeter, so I've included both circuits. If you choose not to use the light, just eliminate that part of the circuit, but keep the resistor. Good luck!
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http://www.hunt101.com/img/197642.jpg[/img]
Jerry