Bob Layton has done a number of variations of the cover to Iron Man #131 over the years. One the original versions featured on the bottom right was rejected by Layton himself, who realized that he "didn't want Iron Man to look like a total wimp against the Hulk," according to a post on his web site. Layton did a fantastic re-imagining of the cover in 2011 featuring a more heroic pose for Iron Man and adding Captain America and Thor in the background. Gerry Turnbull did the colors on this piece that resides in the collection of Brian Cassner.
Source: Bob Layton, Brian Castner, Gerry Turnbull