IMO most people don't pay any attention to a car alarm to do much good in a parking lot when you're not around. So if you get one be sure it has the remote page option. But a professional thief can disable that alarm in about 30 seconds so it won't do much good.
However, as previously mentioned, jimmi jambers and disabling the door locks are a good start. But what's going to stop them from stealing your truck once they're inside anyway? The
Ravelco would definitely fit that bill. So now that you're truck won't end up gone, what's to stop them from breaking your windows and stealing everything inside your truck. Window laminates from
ACE security laminates would help a lot with that.
I firmly believe that with the combination of these 4 items, it would be almost impossible for anybody to:
A) steal your truck,
B) Steal anything inside your truck, and
C) High-jack your truck while you're in it.