ZBrushCentral

Problems with Baking a Rockwall

Hey guys, i made a Rock wall and i use decimation master, but the problem is, this are seperate rocks, how can i combine them to get a full lowpoly model … i was thinking about boolean in Maya, but this destroys every Model, so i wont do that…
any other ideas?
here is a screenshot of the Lowpoly now…

http://prntscr.com/9nk2f5

I hope you can help me guys…(Its for a game…)