Your question is a little vague.
If you want to replace the cassette deck for the CD deck, I don't see why not. If you want to have both the cassette and CD deck, I doubt you'll be able to.
If you need the cassette deck, you could buy an aftermarket changer and an fm modulator, or a tape deck/cd changer from the same company to avoid the need for an fm modulator (plus you'll be able to get rid of the stock unit).
I'm no expert on this, but I doubt you can have both ford decks at once.
Brian
