My 68 stepside was stolen and I think I lost 10 lbs until I found it two weeks later. Lucky they just took it for a Joyride and only damage was the wiring harness.
IMHO, a GPS tracking device is your best bet, Several brands out there and setup is about 100-200 . Looking at this for only 169.00,
http://www.tracking-devices-pro.com/
A friend of mine runs a Buy here Pay Here car lot, and uses GPS on every car he sells. He said he only had one car he could not find since he started using them. He usually calls them in for a free Oil change or some other BS if somebody actually does finish paying for the car, and then takes his tracker back.
The key is to make sure the device is well hidden.