you CANNOT put a LS head on a gsr block, end of discussion.
im really not trying to be a dick but get a clue about whats in your car before u try to sell it, especially after u start arguments about it. and GSR cams will not even come close to fitting into an LS head and for hell's sake lets say they got in there some miraculous way...how would all the lobes on the cams be used when LS heads have a single rocker design?

either way, goodluck selling it