The install is really pretty simple. You'll need 3 parts other than the manifold itself to get the job done. They are a new coolant hose for the front of the heads and 2 plugs for the rear. Here are the part numbers:
P/N:12568478 - the front pipe
P/N:12562788 - 2 of these plugs
I made the swap recently but have been too busy braking driveline parts to get a dyno number so I don't have an exact figure. I do still have an internally stock LS1, though...so the gain is minimal. I'd guesstimate 3-5 Rwhp/tq.
Now a head/cam engine will benifit a lot more. Somewhere in the area of 15-25 Rwhp/tq depending on how radical their combination is.
FYI, here are the results from a head flow test with and without certain intake manifolds. The numbers are in cfm...
My opinion is that putting a larger intake on a smaller port usually doesn't provide much improvement because of the turbulence the step causes. Cemo's post substantiates this. Port matching would definitely help. But grinding on installed heads, I don't know.
Roger- I did not notice any difference in fit with the manifold upgrade, ie. there is not port matching problem. The change and benefit of the 01+ manifold to my knowledge is the volume of the extra manifold area. Just like the pre-01 manifold, it's cross-ram design incorporates decreasing runners that increase velocity like a trumpet but the 01+ runners are larger on the manifold side but end up the same size at the heads. This will create a more dense charge...
I was under the assumption that the LS6 intake ports were raised compared to the LS1's...but I didn't find this to be true. Anyone know for sure?