More than 10 years ago, I bought an Alpine CDA-7894 stereo for the 1977 Jeep Wagoneer I was rebuilding. That rebuild stagnated, so when the factory stereo in our 2001 Chevy Tahoe died, I moved the Alpine head unit over to the Tahoe. The CDA-7894 will read data CD's full of MP3 files (a very progressive feature in 2002), but standalone MP3 players were not yet common devices, and smartphones didn't yet exist. Fast forward to 2013, when I really wanted to be able to plug my smartphone into the truck's stereo so I could enjoy Pandora or my MP3 collection on long road trips rather than lugging along boxes of CD's. The default configuration for that stereo didn't have a convenient audio input jack, but that can be remedied with just a couple aftermarket parts.