If you scout eBay, you can snag a Dodge Caravan or Dakota premium sound system with both cassette, CD, AM/FM stereo with MP3 plugin connection for about $99. It's a direction hook-up to your wiring in the Ram Van. Thus a no brainier for plug-n-play. Even the joystick system for speaker selection works well.
One of the good models is Chrysler Corp p/n P04704383AH or models from the AD to AH era of revision. The sound is excellent from this radio as we have this model in our Caravan SXT. You may need to upgrade the Ram Van 6x9 speakers for the doors and rear. The dash corners at the windshield have the 4-inch tweeters.
The unit has to be the square one. The rounded side types will not mount correctly. 1884-2002. Models from 1998-2002 are the better units.
Here is the square one pix.