I know the original dealer for my GTS because it is in the original owner's manual along with the original owner's name. I know the second dealer because the second owner told me and the car still had a plate frame from that dealer. I also have two broadcast sheets and the fender tag. With that said, I still wouldn't add a repop window sticker, even though it would likely be accurate.

What I would suggest is to find the newspaper where you think it was originally sold. Many dealers advertised cars with VIN numbers when new. Here's an add for a bunch of interesting cars...Having the original license plate also can help. That's how I found the dealer that sold my son's Dart convertible used in 1970.