Yes from 2002+ GM had LS6 vice LS1 blocks, they also had the LS6 intake manifold with them also.
so heres how to tell. the LS1 manifold isnt flat on its bottom side and has an "X" pattern on the plastic. the LS6 manifold is flat on its bottom and has a SQUARE pattern on the plastic. Im at work so I dont have picks but if you need me to clarify further let me know