Well we don't know about all the wiring on your truck. If it's all done per original diagrams or other methods, Assume a 327, some kind of harness, a "original" ignition switch. Maybe ballast resistor, maybe an ammeter and so on.
The switch has markings on the rear for the terminals:
1. ACC
2. IGN 1
3. IGN 2
4. START
5. BAT
There is a hot wire to the ignition switch BAT (B) terminal. That would be the one you would use to put the toggle on. You could also put it on the start wire. I am not exactly sure what you said. I have to be very careful to understand. It's easy to misunderstand each other during wiring assistance. So another way to say it is: Remove BAT wire from Ign switch BAT terminal and attach it to one side of toggle. Add a jumper from other side of toggle to Ign sw BAT terminal.
If that does not work, you have some screwed up wiring somewhere.
