Sony CDX-MP40 (X-PLODE)  From some outfit on EBAY ($80).  Very plain looks and no "Atari" graphics on the face.  It was a store return. Can't remember what led me to believe it would fit. I did spend some time researching.  I think I checked factory dimensions on it at it seemed like no problem.  I did have to push the rear VW mounting support out to the way. I was worried that my new antenna with traditional plug would not fit against the air vent. Once again no problem.
  Dramatic improvement over the stock Heidelberg--cant believe I didn't do it sooner.
  I did have to pay $18 for the new harness adaptor.
  Mine is an MP3 also, LOTS of music on one CD. Less flipping etc. Remote is nice to control from outside the van or in bed.

  I hear "Circuit city" has a "dump" auction site if you can find it.

  Good luck,
  Chris C 90 MV