Ed - my log book says it's a 2.5, as far as I can remember this refers to the model not the engine size. Like referring to YJ's as hard tops and TJ's as soft tops.
Plum - the carry over bit Mark was referring to is when Chrysler 'used up' older engines in newer models, 258 the cylinder capacity of a 4.2l in cubic inches. They did this with some YJ's, using a 'CJ engine' in the new models.