Wrapped/Tileable geometry in sculpt mode?

Okay, so I got this tileable/seamless texture of a rock wall…

Now I need a normal map to go with it. I tried a plugin for photoshop that’s supposed to generate one from the image, but it ended up fresh-out-the-butt crappy. So I resolved to put the effort into making normal maps “THE REAL WAY” by baking them from high-poly models onto a flat plane. (Not sure if I’m using the word “baking” accurately in this scenario, but you get the idea.)

So I took this texture and applied it to a plane in Blender (2.66a) and used the Sculpting mode to actually bulge out the rocks for detail.

It’s works great except for one problem… the geometry needs to wrap/tile around the edges the same way the texture does. I tried creating linked duplicates of the object and making a 3x3 array, hoping I could edit them all simultaneously (focusing on the center one), but even if I select them all before entering sculpt mode, it still only let’s me edit one of them.

So my question is, does anyone know how I can pull this off? Has a 3rd party made a plugin/add-on for blender that could help. Any insight would be great. Thanks.