Update on my post yesterday about the plastic engine covers and not fitting properly on the drivers (left side). Seems there was a change somewhere in the life of the 4.0 in the design even though both have the same part number. In the attached photo the ones off my '99 (broken) have a scallop cut at either end that the replacements do not have. Guess I will repair my broken one and sell the other on eBay.

 

Had the same problem. Look on the back of the part and you will see where to cut out the piece by the overflow tank. It will fit then.

 

+1 on Dave's comment. I cut the replacement cover with a saber saw with a fine blade to match my original cover, then sanded the edge. It looks just like the original. It took about five minutes.
Good luck.