There has to be a trail - paper or otherwise. Maybe you're the third owner, and the previous owner can tell you who the original owner was. Maybe you have sales documentation, or the original owner's manual with the buyer's name and address. Depending on the state, you can sometimes get old DMV records. Other than that, I don't know how you'd go about it.
Easy, I got mine from the original owner & we've known each other 20 years. If you're diligent & really want to know, you can fight through DMV & some places on-line. Kevin Marti does them back to '67..
When I got my 68 fastback the guy that sold it to me showed me a compostion book that an old owner had-this guy logged everything! (1156 light bulbs) costs/parts/dates. when I got home and started to go thur it-I started to recognize the guys handwriting- here a guy who worked for me had owned it 22yrs ago!we had talked prior on how I always liked 68 fastbacks-he said he had owned one 20 yrs ago and had sold it-I don`t live in a small town either-but it is a small world-he also knew and purchased it from the original owner
"All vehicles running and stationary get the same miles per gallon" *zero mpg*
There have been several owners between the original owner and myself. However, it seems none of the others cared for Her like me. When giving her a thorough cleaning, in one of the trunk wells by the rear quarter deep down inside I found some credit cards (long ago expired) and an Auto Club card. They were caked with grime but cleaned up fine. I then did and internet search for the name on the cards and found a name and phone number.
The conversation went something like, "Hi, you don't know me but did you use to own a Mustang?" "Yeah, what year?" etc. etc. etc. He had some interesting tales to tell about when he owned it and who he sold it to. He asked me to contact him when the restoration was done so he could see Her again!