It's important to note (and I am a Devils fan, so homer glasses) that a large majority of Stevens' hits would still be legal today. The main reason why hits from his era are no longer legal are:

• Contact being made to the target's head. This is where some of his most highlight-worthy hits would have gotten him suspended in today's game, especially since he knocked guys loopy on these type of hits.
• Elbowing is called more strictly nowadays. For the most part, Stevens wouldn't have had much of an issue here. The Lindros hit was one of the few big hits where he let his elbow loose. He usually had textbook bodychecking form, leading with the shoulder, elbow tucked to his side until contact is made. It's also worth noting that in his career, he had a ridiculously low FOUR elbowing penalties. Even with more lenient rules, if he was elbowing people regularly he would've racked up far more than that.

The majority of his hits, the hundreds that didn't make the Top Ten lists, were textbook even by today's standards. The majority of his hits didn't send a guy stumbling back to their bench either. But every once in a while, you get a "perfect storm" situation - high speed puck carrier, head down (not looking at the oncoming freight train), distracted by the strong side defenseman or winger... Even your average high school defenseman could lay a decent hit in that situation, but when you have one of the most physically dominant and intelligent defensemen in league history doing the hitting, you're going to end up with some scary looking highlights.