Like I said last night, deterrant is delay, delay, delay.
Big old piece of bike lock chain tight round the clutch pedal and steering wheel, likewise with the gearctick and hi/low lever. Fuel shut off solenoid by pass, starter bypass. Tracker.... wiring up the alarm sensor to loud thing. Motion sensor lights, security camera... Internal camera. Line lock on the brakes (I think I have one somewhere if you want)... hoofin gert big dog in the truck - or even a Jack Russell with an ASBO. Nothing is thief proof, but a thief needs a quick steel