OK everyone, I just downloaded the wiring diagram for the shaker 500. After studying the diagram I think I have decided to tap into the #2 wire on plug J1. What do you all think??? Is there a better wire to tap into? Here is the first picture of the wiring diagram

 

Here is Pic #2

 

And #3 the back side of the shaker 500

 

The wire in your first post should be the right one. Get a multimeter and find a good ground. Set the multimeter to 12 volts dc put the positive electrode on that wire, turn on the ignition and if you get 12 volts your good, turn off the ignition and it should go back to zero. If that happens thats the wire you want.