Originally Posted by ViRaLuNdEaD
If I remember correctly Wanted: Alive or Alive is not story related and is tied to the bail bond missions and bringing one of them in alive. Not sure if they are replayable. Someone else might know.
No, they are not replayable. But if you don't remembered doing any, I suggest you take a look in the quarry east of Sandy Shore Airfield and Prison (other side of the HW).
The first Bail bond target is there. Near the first time you play as Trevor (beside Prologue), Maude send you an email with a description of the first bail bond... but it rapidly getting forgotten with all the other missions (and spam email). The target will try to flee in a van, just blow out tires and he will give rapidly.
There is five bail bond missions in total. You can surely bring at least one alive. Remember: if the target run away, take a pistol and shoot it in the ankle. Best method to NOT kill him.
If you have already killed all the targets... I think your only option is to start a new game and play until you reach that point in the game... which shouldn't be too long.