Have you tried Crutchfield.com? If you use their "find what fits my car" option, then click on "iPod in your car", you can select your ipod and radio (factory or aftermarket) and it will show you your options.
I have just bought a 2006 Tribeca Subaru and want to wire my IPOD to it. I had a Stereo shop try wiring it to the FM modulator and running it through the headphone jack. The sound was poor and sigal not strong enough..ie low volume. Any suggestions that have worked?? Thanks STU