Check out a pack from Staggart Creations.
Staggart Creations released a useful tool for replacing a set of objects with another. The editor works nicely if you want to swap out placeholder objects with prefabs.
Among technical features, the tool supports redo/undo actions and retaining layer, tag, static flags, scale, rotation, and prefab overrides. You can access the tool through the "GameObject->Replace selected" menu.
Staggart Creations provides unique and user-friendly game assets for game developers and artists. Visit the Unity Store Publisher profile to check out his assets.