i would only get the headers if you are serious about modding your car. they will fit a 3L. they also work best with a good intake and a good exhaust setup.
the reason i say only get them if you are serious about modding is because they are expensive. if your not that serious about it, just gut the precats.
also, only egt the MSDS headers, stay away from the weapon R headers, they are junk and dont fit right