Does the 4 WD connector that goes to a dummy plug on the back of the dash, have any power and can it be used for anything else?

 

The connector behind the dash is likely inactive if you have a 2wd, since the PCM needs reprogramming to work.
You could install the switch and wire up your own wires to control anything you want.
It might be clever to have an anti-theft switch concealed as the 4x4 switch.
2wd => won't start
4x4 hi => won't start
4x4 lo => start enabled

 

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