Thanks so much for the work you're doing. I have friends at the Library of Congress Motion Picture Conservation Division and one of them told me that although ANH was added to the National Film Registry, Lucasfilm would only supply them with a print of the SE. They do have access to an original 1977 print (pre Episode IV) from which to make a copy, but have yet to actually pursue the matter. Even though it would be a negative made from a print, at least the original would survive in some form. I find it hard to believe that Lucas would completely destroy the film that made him a gazillionaire.
Anyway, fantastic work so far. I look forward to the final results. Keep the faith.