Superman - "Hercules in the 20th Century!"
Out of the dim past, have come the renowned names of super-strong heroes... Atlas, Samson, Goliath, and others! But mightiest than all of them was another super-muscled "Superman" who existed long ago... who suddenly appears in the modern world! And the people of Metropolis, who already are familiar with the mighty feats of Superman, now witness equal feats performed by the strongman of the past in... Hercules in the 20th Century!
Main Story: Lex Luthor builds a time-machine to bring Hercules to the present to use him to stop Superman. Hercules gets wise to Luthor's plan and helps Superman stop Luthor, and then decides to stay in the present and falls in love with Lois Lane.
Reprinted in Superman #239 & Showcase Presents: Superman #2.
Supergirl - "The Three Super-Heroes!"
As Supergirl, Linda Lee is constantly getting into one startling adventure after another! But one day the surprises come even quicker, and are more astonishing, than usual! A Baffling series of amazing encounters has the Girl of Steel wondering what in the world is happening to her! Who are the three strange teenagers who mystifyingly enter her life, and what is their purpose in helping her hide the secret of her real identity? The answer is even more fantastic than she could possibly guess, and leads her 1,000 years into the future, to a stunning surprise finish in the amaze-a-second adventure of.... The Three Super-Heroes!
Co-Feature: The Legion comes to the 20th century to meet Supergirl and invites her to come to the 30th Century to apply to join the Legion.
Reprinted in Action Comics #334, Adventure Comics #492, The Legion of Super-Heroes Archives #1, Supergirl Archives #1, Showcase Presents: Supergirl #1 & Showcase Presents: Legion of Super-Heroes #1.