You can use a DPDT switch, using one set of contacts to break the "start" wire to the starter from the ignition switch, Then use the other side of the switch to ground out the points, by connecting a new wire to the ignition coil to the same spot on the coil as the wire from the distributer connects (this is where a Tach would connect). This way even if someone does try to hot wire the truck and jump the starter under the hood it will take a while to figure why they have no spark! If you have an electric fuel pump you can also put a switch on that too.