With a totally stock LS block you can probably make 230 or so safe whp with a turbo, maybe a little more. On the other hand a GSR running 8 psi will easily put down 260 to the wheel. The GSR head flows more than the LS head, and VTEC helps make the turbo even more happy.

If you want to just make 230 whp, then an LS will be fine. If you want to make more than that, then you need to get a GSR.