Yes you can swap it over. I have an LS sedan and got the sub off of Ebay and had Circuit City wire it to a 150 watt amp. It actually sounds better than a coworkers facroty 7 speaker setup. If you do any sub install Dynomat the truck first for an even better sound quality. Many people dont do that and that is why it sounds like the windows are about to rattle out of the car.
But yes you can put the Pioneer sub in a model not equipped. You will have to get her bolts to mount the speaker in your trunk. And a tip to install the nuts, get a foot long piece of hose the same inside diameter of the nut and put the nut in the hose to start threading, then you can use a deep well socket to tighten the nut.