You are going to need a harness that plugs from the back of the tape player into the CD player and from the CD player on to the speakers, unless you have an amp (which I believe anything with a CD player has) in which case you will need the harness to plug into the amp.
I'd check eBay, audio shops, swap meets, junkyards, online classifieds (for those who are no longer using theirs due to aftermarket radios), and lastly a Ford Dealership/Service center.
I'm including a bunch of attachments (actually one big .pdf file) for the radio wiring I have I printed out from All Data a while ago. Hope that's okay. Hope it helps.