Has anyone used a modern Sirius chrysler antenna on an old Mopar?

My Dart "accidently came" with an aftermarket radio and a USB connector. AWESOME!!! Just load up music on the USB stick and LISTEN!!

I'm thinking about "digging into" at least one of my other radios (Cassette AM/FM) and tapping into low level audio so I can jack in an MP3. I tried the Cassette adapter with "very mixed" results. There is no decent AM/FM around here, FM is very spotty