If you put that in the spare tire well, all its going to do is bounce around and sound horrible. I'm guessing you have the mach 460 factory system? If so, no, it won't fit. If you have a full aftermarket system with the large black enclosure removed the you have a fighting chance. My suggestion, find out EXACTLY how much airspace is inside the enclosure you have, then build or have one built for you to those specs and using the same port, tuck it nicely under the rear deck and fire that puppy toward the rear of the car. Even with the factory system still in there, a good installer can still fix you up nicely with a custom enclosure.
If you really like the Kicker sub then I would suggest buying the speaker without the enclosure and going custom, especially with the factory system.