Not sure this would help too much. As Six Shooter was eluding to, if you simply supply the +ve side of the coil with a 12v supply directly from the battery you can almost ensure spark. With carbs and non ECU control ignition, there is very little you can do to immobilise the engine.
I have heard of people having an alarm and tracking device. The aim is that when the alarm is activated a SMS is sent to your phone, you can then track the car via GPS. While this doesn't stop the car from being pinched it sounds like it would help to recover it.
When do thefts tend to occur, I imagine when the Car is parked at its usual location, home, so I agree that parking in a garage with additional cars parked in drive sounds great but not always practical.
Just my thoughts.
Mick