Lyle, I gave out my last Mopar cassette chassis some time ago...
Best I can do for you is to either recommend a good salvage yard pull (and they don't just leave them in, they sell a lot of OEMs) or try something like this:
http://replacementradios.com/ as the Diamondstar Crew has made some nice Rammy Jam sets over the years and the chassis size and mounting style is probably pretty close.