WOW! That's QUITE a jumble of wire in your photo!Give THIS a try... 
You can use your choice of "MY" diode, "BobM's" "idiot light", or "JohnT's" resistor anywhere that's conenient in the wire feeding power from the ignition switch to the alternator's #1 "switched excite" terminal. You only need ONE of those three options, and ALL work EQUALLY WELL. If you want an "idiot light" in the dash, go that route. USe a #194 lamp, or one of equivalent current draw. If you want to use a resistor, go that way, but be advised it will get HOT, if the key happens to get left on, so you need to mount it so that it can dissipate the heat without melting any wires. That's why I almost always use the DIODE... it provides protection to the alternator if there's a problem in the high-current part of the charging system wiring, and prevents the engine from "running on" when the ignition is switched "OFF", but it doesn't get HOT, so it can simply be covered in heat shrink tubing, and taped up along with the other wires in the harness. Questions?
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