Sources for the fact that L&S did not write the silly lyrics include Hound Dog: The Leiber & Stoller Autobiography, by Jerry Leiber and Mike Stoller (Simon and Schuster, 2009)
Thanks for the source. The Hound Dog chapter goes from p61-66. Unfortunately, on Google Books pages 65 and 66 are missing, possibly the pages that are mentioning the Elvis version. Do you have them by any chance?