Per Nick Caputo, Kirby pencilled the cover, although Ditko either did rough pencils on the Spider-Man figure or revised Kirby's original figure. Ditko likely touched up the Giant-Man figure as well, with Chic Stone inking the cover. Nick has an examination of the cover at his blog: http://nick-caputo.blogspot.com/2012/05/avengers-11-cover-mystery.html
Iron Man appears on cover but not in story.
Letters from Thomas Bloyen, John Hudson, Barbara McCasland, Tom Conti, Masataka Hirota, Ruth Doyle, Robert Linderman and Al Russell.
credits per Nick Caputo, April 2014.