In SUSPENSE, Iron Man always was the lead story, Cap the back-up, UNTIL issue #98, when they began to alternate. The covers had been alternating a long time before that.

In ASTONISH, GIANT-MAN always had the lead, HULK the back-up. Later, SUB-MARINER was always the lead, HULK still the back-up, unti issue #99.

Similarly, in STRANGE TALES, HUMAN TORCH, HUMAN TORCH & THING and NICK FURY always were the lead, DR., STRANGE always the back-up, until a few months before the book split into 2 separate magazines.