I can't remember exactly when production of the 4.0L inline six ceased, but I'm sure it was when aluminum V6's began appearing in Grand Cherokees. I know that the reason for the switch was because the cast iron inline six was too heavy to keep up with ever tightening CAFE mileage regulations. I was once told that the inline six would bolt right into a '65 Rambler ambassador with little or no modification as that's what the engine was originally designed for. My last day at the plant was October 22, 2010. All that remains is an empty brownfield and a plaque that tells of where the Jeffery, Nash, American Motors, Chrysler Engine plant once existed. At the museum in Kenosha is the last 4.0L engine off the line. Everyone signed it, I think my name is near the distributor boss. Larry W