Hey there. Welcome to classicbroncos!
Yeah, you're not going to have much luck with most online listings, because old vehicles had much shorter VIN's than they've been using for the last many years now.
So much so that even some DMV people will insist that you're crazy and that's not a legit number and to go away and not come back until you grow a few more numbers!
They're too young and they apparently don't teach people at many DMV's (not just here in CA) that not everything is a new vehicle.
If you can't verify that it's currently licensable in your state, or it's not stolen, then most will say walk away. I hate no title situations, but some of them work out fine.
What state are you in? That's probably the single biggest stumbling block, or advantage you can have. Some states are just easier and don't delve too deeply into the history of the rig.
Good luck. Sorry I don't have any direct info for you. But let us know where you are and someone from there might have the answer.
In the meantime, back to the top of the page for ya...
Paul