Bridwell, Schaffenberger and Colletta send Captain Marvel to Niagara Falls in Shazam! 29 (May/June 1977).
The story begins as Sivana kidnaps Stinky Printwhistle, determined to make the man turn into Ibac once more. He winds up needing Lucifer himself to provoke Printwhistle into saying the magic word. Lucifer leaves the story immediately after this scene, though.
Instead, the story goes for broad comedy, as Sivana introduces Ibac to Aunt Minerva, who immediately starts trying to pick him up.
This is all just fine with Sivana. He only wants the other two villains to distract Captain Marvel while he proceeds with his big plan to blow up Niagara Falls, using a bomb in a barrel. Sivana does not count on Ibac trying to hide from Aunt Minerva in that same barrel, removing the bomb first.
Ibac winds up turning to Uncle Dudley for help, and they use the disco light machine to talk to Solomon, about how he dealt with having four hundred wives. Ibac realizes he can ditch Minerva simply by turning back into Printwhistle, and does so. As the story ends, Sivana discovers that Ibac had placed the bomb back in Sivana's lab, which blows up.
Sivana is captured by Captain Marvel at the end of this issue, but is back in the next one anyway. Ibac and Aunt Minerva are next seen in the Shazam series in World's Finest Comics, Ibac in 1980, Minerva in 1982.