Yeah, it would be hard to find the original owner, unless it is a one owner car, but I doubt that it is. Like Jim said, if the VIN data plate is missing, then check the inner fender on the driver's side. It's stamped there in a cut-out of the fender. Here is where to look. But, you have to realize that these old Mustangs have been modified over the years by previous owners, so there is no telling what you have. As Jim mentioned, there are no written records before 1967 as recorded by Marti. You are just going to have to accept what you have. If you give us some pictures and descriptions of what you have, we can pretty much narrow it down.