Iron Man #21

In "The Replacement!", Tony Stark, struggling with a failing heart, takes the unprecedented step of finding a successor—Boxer Eddie March—to don the Iron Man armor. When March steps into the role, his own serious health issues threaten to derail the mission, forcing the original Iron Man to intervene in a high-stakes clash with the Crimson Dynamo. Written by Archie Goodwin and illustrated by George Tuska, with inks by Joe Gaudioso and letters by Jean Izzo, this 1970 Marvel classic features cover art by George Tuska and Mike Esposito.