Seeing your thread stirs up thoughts of me chasing down my '78 Bronco I had in high school. I loved it, my parents convinced me to sell it as they hated to see me sink money into it. I've regretted selling it ever since.
Someday when all the kids are grown up, I'll chase it back down.
Wonder if you could get a carfax done on it? I actually saw a show on tv where this guy makes a living chasing down cars for previous owners. I can't remember what it's called but googling should yield you some good results.
I would concur: carfax is probably your best bet. It may at least show the last time and place the truck was serviced.
I'm fairly literate in the auto auction industry and I can tell you that CarFax is the closest thing to a central database around. You can try your DMV but (if they're allowed to do it), it'll probably cost you and it won't be any help if the vehicle is in another state now.