The MJ was made from 1986 through 1992. In '86 it was available only as a longbed and came with the 2.8L or the 4-cyl. '87 saw the intro of the shortbed, as well as the 4.0L (same as the XJs).
There are MJs around, but far fewer than there are XJs. Perhaps that's why I feel like I have to "save" every one I can get my grubby mitts on. They were great trucks, and IMHO would have sold a lot better if AMC had only offered an extended cab version.