A dealership in my area has A book of all invoices for all cars sold since new. I personally saw it about A year ago when A member from this board who lives in Canada asked me if I lived nearby and could talk with them about his car which was sold new at that dealership in 67. They had his stuff!! I am planning on going back soon and asking if I can look through the book myself and make copies of any possible "special" cars paperwork they may have.
Tommy