One of the biggest differences if Johnny didn't die would have been Dallas Winston. Most likely, if Johnny had never died, Dally never would have committed suicide.
This means that Dally might have continued his life as it was. A life of crime and hatred. Simply, things could have just gone back to normal.
On the off chance, Dally could have learned something from the situation and could have learned something from Johnny about how to be a better person. Because of his love and respect for Johnny he might want to try to change the way he lives. Especially after how close he came to losing his closest friend, he might become more attached to Johnny and more caring towards Johnny.
Of course, Johnny would be crippled for the rest of his life. This could cause Dally's feelings towards Johnny to change. Especially because Johnny would have most likely gone to jail and all of these different things could affect the relationship between the two of them.

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What if Johnny Cade Never Died?
RandomIn this book we look at Johnny's death and how the Greaser's life would have been affected if he never died. (Clearly this book has spoilers about the book "The Outsiders").