I'm pushing it with a 3.3" pulley and I'm keeping that pulley on after headers. I might try a 3.2" on 104 race gas at the track to see if I can shave a little time off, but not for street use. So that can give you an idea of what size pulley he needs.
Too many kids throw on 3.0 or smaller pulleys thinking they will get insane amounts of power, but without the airflow moving through the engine that they need it only creates heat and lots of KR...therefore the car is slow as hell.
To run the 3.4, I recommend a full downpipe/cat/u-bend removal combo along with the CAI. The downpipe on the GP is very small and restrictive, and the u-bend makes it a million times worse. Mufflers will only help a tad, but it would sound nice.
Check out www.3800performance.com for an R/T downpipe. Or you can find custom ones if you check out clubgp.com. I bought a custom setup.