@Ricko1966 is correct. And afaik, there’s no “high tech” solution as these vehicles don’t have an ECM that can do the same as newer vehicles. That Guard dog is. Good simulation of that provided the thief can’t find it and swap a couple wires.
Same goes for any homemade system. They rely on creativity and hiding the “kill switch”.
We all have our own methods. And anything is better than nothing.
Additionally, if one thinks there’s any real risk of theft. IE gets driven and parked in urban areas, a good supplement to a kill switch of any sort is a gps device. Could be as simple as an AirTag.
Been thinking about something for the 77. Got the 86 figured out and it has a unique condition that a truck of that year would not have which helps with the stealth/confusion if it were hot wired and stolen, it wouldn’t get far if the switch is activated.
The Guard dog seems like a nice device for hands off approach if it and its wiring are “hidden.”