Some useful information i ran across while looking for ways to identify a 4.0L for DIYJ. The casting number is cast into the head, and found on the drivers side. The year ranges follow:
Year............Casting No 1987-90......53005535 (8933002665) 2686 1991-95......53008405 7120 1996-98......53020569 0630 1999-04......53010449 0331