I should add for anyone else that may find it useful, when i checked my 87-88 parts catalog it lists the digital 4 speaker radio for these trucks as being part number MB488544 this is incorrect since it is the orange illuminated J892 used in the Montero/Raider that MrPaco mentioned in a previous post. The radio he bought can be found in Colts and Colt Vistas of similar vintage and so far we haven't been able to figure out what the difference is between these radios and the MB541097 J989 4 speaker ones that came in our pickups and strangely my catalog doesn't even list the MB541097 at all for any vehicles even though i know mine came from an 88' Ram 50. I was talking to MrPaco earlier and I had mentioned that the J891 may have a slightly higher power output to drive bigger speakers in a car or a different EQ circuit board to change the sound output to suit a larger interior but this is just a wild guess.