You should be able to make them all the same mesh without adding tris. In your 3D modeling tool just combine all the meshes in to a single object. For prop-sized objects, that's pretty much the rule of thumb, 1 object and 1 material if possible to keep your draw calls low.
For more info: http://docs.unity3d.com/Documentation/Manual/OptimizingGraphicsPerformance.html
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