Shula wasn't exactly a pass-happy wide-open coach before Marino either, aside from a couple of Griese seasons late in Bob's career. Noll could've and would have adapted, like he did when the league opened up the passing game starting in 78. Steelers took advantage and passed more, becoming fairly "wide open" compared to previous years (as did most teams, hell by default all teams across the board were going to get more passing yards...not the best argument to make but they weren't pounding it up the middle with Franco while throwing 18 passes a game after '77). Whatever the case, if Shula could adapt to Marino, Noll could have as well, and Marino would have fit like a fucking glove in Pittsburgh.
Aside from Elway, Marino, and Kelly, whichever QB the Chiefs took would have busted. Eason or O'Brien would have been the Blackledge of the group, and Blackledge would have been O'Brien or The Guy That Got Destroyed in Super Bowl XX.