Brass is right about subtle differences over the years in 4.0L. The engine I just pulled is a 98, the engine I'm replacing it with is an early 90s that was remanned in 04 and there are enough slight differences that I have to use many of the old parts as they aren't quite close enough to use the new parts. The header is one of the parts that don't go from one to the other. Those are OEM.