I've got a set of brand new never installed front Mopar Molded Splash Guards for the 99. These fit the Durango or Dakota "with flares". I had bought the complete set F/R but never installed the fronts due to installing molded running boards. If this is something you may be interested in, I can post a picture. You'd need the rears though to complete your set. Could probably do $20 shipped USPS.
I also have a K&N FIPK for the 5.9 Durango. The tube is brand new never installed, (updated version) the rest of the kit is slightly used but like brand new. I know it is not on your list but thought I would throw it out there. I'd do the splash guards and the kit for $100 shipped. Can get pics for this as well.
These flaps will not fit unless you have the factory wheel flares. Below is a picture of a Durango with flares and another of what the flaps look like. The factory instructions and hardware are included. Again, these are for the front only so you would also have to buy a set for the rear.