40s? That was still going on in the 60s. Think about Journey Into Mystery, Strange Tales, Tales of Suspense, and Tales to Astonish. Those four were renamed The Mighty Thor, Doctor Strange, Captain America, and Incredible Hulk. So that Immortal Hulk #2 cover may say #719 on it, but it's not the 719th issue of Hulk. A bunch of the first hundred issues were actually Ant-Man and Sub-Mariner.