I`m a police officer in the auto-theft unit, heres what I say-
Any GM vehicle made in the year 1977 to 1996/97 with a tilt sterring column can be taken in 5 seconds or less. To protect your vehicle from being stolen a visual deterant, 'the club' may be used. But, the club device can be bi-passed in about 4 seconds, its just that, A VISUAL DETERANT.
I recomend purchasing a alarm system that deactivates/disbales the ignition when it is set off. This is so that even if the steering column is compromised, the alarm system will have disabled the vehicle from being started.
No matter what type of alarm system is on your vehicle, if they want it that bad, it will be taken with a tow truck. Heres where Lo-Jack comes into play. It works great, but the vehicle must be reported stolen for it to activate. If this happens it is only a matter of hours before the theifs locate the Lo-Jack and take it out, throwing the transponder in a lake or throwing it down he sewer drain.
Get a loud alarm, that disables the ignition.
My personal 95 caprice w/ the corvette engine was stolen from accross the street of my police station, and I never saw it again. I know the feeling.