Bill,
Go to
http://www.bookfinder.com and put in search terms for author: Robert W. Elliot and Title: Lefever and you'll get a hit on both of his books about Lefever history and craftmanship. The most recent version is the best, "Uncle Dan Lefever, etc., etc." and,if you subscribe to The Double Gun Journal you can find an ad that will get you an autographed copy directly from the author. Also check the book rack on this site!
Second, Cornell Military Publications, Abby Mouat, has reprinted most or all of the Lefever catalogues from 1872 and they have much Lefever lore in them. I just got the 1889 edition and it's very informative. The DGJ, of course, has a few more than several articles on Lefevers.
Best in the New Year,
Tim