The gas and LP motor in the 6000 is 223 cu in
But the diesel is a 241.7 cu in (242) (4.0 L) 6 cylinder motor.
Ford used a Dorset 4.0 (242 cu. in) diesel motor in their P-3500/4000/5000 trucks from about the same time frame. One BIG problem is the Dorset 4.0 was a 4 cylinder motor.