As said the D1 is a single DIN slot. Most new stereos come with a cradle that the stereo itself slips into. Even if it is smaller it is fairly easy to pad or bolt the stero cradle in and then slide in the head unit. Worst case scenario is you may need to pad the gaps with some foam or cut out a fascia from some scrap plastic, but only if there are any gaps, which is unlikely/ Most head units also come with a surround that is clipped around the head unit to hide the cradle and gaps anyway.
I would buy Pioneer, Alpine, JVC or maybe one of these Eclipse units
Eclipse - Alberts Online - Albert's Car Stereo - Car & Marine Entertainment Specialists

