Best bet is search on the internet.
IMHO...For regular salvage yards, yes....but for vintage cars & trucks, in my experience, you have to do a lot of searching, asking strangers, driving in areas that no one knows about, and many of those property owners don't even know what a computer looks like.
You could also look at satellite-view maps and spot clumped-together rusted vehicles in desolate areas...especially in the Midwest.
btw..my brother once had a '46 Suburban, and the previous owner claimed to have found it in the middle of the desert in Nevada. He flies one of those single-passenger short-range planes to look for abandoned vehicles for later retrieval. Not sure if I believe the story, though.....