The IOH Occlusion System is available for use on any version of unity and is highly customizable.
All you have to do is drag the IOH Occlusion System into your scene and use the custom menu editor for your liking then the scripts do the rest.
No need to pre bake or to set up stuff in a grid all you need to do is press the play button. If you do however have dynamic object creation in your script just call a simple method from the IOH Occlusion system to have the system search for new objects and add the scripts needed to all the changed objects.
Things coming soon:
Dynamic LOD system to help with the rendering and make it much smoother and faster.
Faster Occlusion system with less minor scuffs.
Current Version: 1.2