No offense Gary, but I'd leave the PO alone. Unless it was some super special or rare old classic, once it's gone most previous owners don't want to know anything about it. They sold it for a reason and moved on. Likely wasn't any nefarious reason, probably just didn't fit their needs or interest anymore, but it's the past for them.
I can say for certain that if I sell a vehicle, I don't want a future owner hunting me down talking or asking about it. I've moved on. If I wanted it, I'd still have it. If I wanted another, I'd start over fresh and build from what I'd learned the first time around.
I sold it because I was done with it. I'm happy that next owner is getting good use out of it, but I want nothing to do with it anymore.
On the rare ocassion that the previous owners do want updates, they will usually know it's being bought as a project and tell you that they'd like you so show it off when you get done with it.