Then LS it is. Anything stock looking, 2bbl and crappy factory exhaust mean no performance, don't bother if that is the criteria. So no 4bbl and intake off a factory 4.1 V6 RWD? I believe they were 81 to 85, CCC and EGR. Your factory ECM should run it no problem. I would start with a 2004R and upgrade the gears to 3.42 plus.
Even with LS swaps, only the expensive Erod crate engines from GM are legal to swap in for CA as they come with the proper paperwork. Used normal production LS engines from junkyards are not easily legal to swap in due to the complex OBD2 emissions that must be completely swapped over intact in CA. That includes the gas tank and dash, plus no computer tuning as that is considered tampering.