Making a car difficult to steal

You can jump one wire from the battery to the coil and jump the starter relay to start it on most of these cars, so ignition cutouts are pretty much pointless.

Fuel cutout are a little better, but don't stop towing.

Locked brakes on all four corners is better but not really feasable to implement. (blead down from premature rubber parts failure would not work out well)

That's why I suggest grounding the tach/ coil neg wire

You can hide the ground/ switch to the electric pump relay

If you have an electric pump you could install a dual tank valve and plug one port, then rig it so that it has to be powered to allow fuel to flow

These kind are not very expensive

http://www.tomsbroncoparts.com/page...0/09/early-bronco-electric-selector-valve.jpg

and you can buy solenoid fuel shutoffs.