MSD-How are you guys hooking up your ON-OFF switched wire ?

I used the Coil wire from the Ballast resistor like Kid said for the "Switched" power lead. I also run the main(Thick) power lead to the battery side stud on the solenoid and fused it with a 30 amp fuse and fuse holder at the stud. Once inside the car I added a 30 amp circuit breaker about 5 inches from the MSD mounted on the passenger kick panel. My BTM is the same way but has its own dedicated main(Thick) lead with fuse and circuit breaker. It too is mounted on the kick panel.