Cut off switch
 

I'm wanting to install a cut off switch or anti theft device to my 2001 f250 7.3 does anyone have any ideas ??

If you choose to pick a place that prevents fuel from flowing, someone could always run the batteries down trying to get the vehicle started.
You might consider interrupting the power to the starter or the ign system so it would give the impression of dead batteries at which point any further attempts are discouraged especially if they think the starter is defective.

pull the IDM relay

Do u know where it's at

Google search (or better still - owners manual) .................

https://www.google.com/search?q=2001...e2_eq0mdDIWgM: