Traded my Ranger in a few weeks ago, and my P.I.E. auxiliary converter FRDN-AUX is one of the items I pulled before hand.
It's used, but in great condition. I had it in my 2003, but it would work in other years depending on which radio you have. It will allow you to connect an audio source via RCA inputs - I used my Zune, which just required a stereo headphone to RCA cord (sold seperately).
My eBay ad is here: