Here's a letter listed on Abebooks: it's from Welles and is interesting in that he believed he was going to finish Quixote in 1966:
Madrid 1 page, quarto November 8, 1966, 1966. Written to newspaper columnist Leonard Lyons of the New York Post and signed in black ink, "Orson" In the letter, Welles writes: ".The European press on 'CHIMES has been absolutely sensational. This in sharp contrast to the very negative approach in America - that is, with one shining exception! That was a marvelous fanfare of trumpets and much appreciated, believe me. I think I told you about finishing 'DON QUIXOTE this summer. Im also producing 'THE SURVIVORS by Irwin Shaw and Peter Viertel. You may remember this play some years ago in New York. Brooks Atkinson liked it better than 'STREETCAR, but he was alone, and the all-star cast were all playing the wrong parts, so it wasnt a hit - this time were going to try to make it one. I acting but not directing - this one of the series of features Im going to produce with my Spanish associates during the next couple of years."