Can I assign a group of meshes as one LOD level?

I am talking about how there is different levels you can set to percent LOD, and you put in lower and lower detail model, but does it have to be a single mesh? or can u assign a group of meshes to a single % slot?

The reason I ask is because the model is broken into modules so I can prefab parts that are the same... which arises another question, (if the first question is possible): Can you have several of the same prefab in a LOD % group?

I have Unity 4 Pro.