I had molded plastic mud flaps on a Envoy and the wife cracked a back one backing out of the driveway into a snow birm the Plows left at the end of the driveway. I am interseted in the Factory flat rubber ones because of that incident. I have a limited 08 with running boards (not Power). I noticed that various sellers ask what model Expy you have when ordering, how come? Are they not universal fits?
Ford made molded plastic mud flaps for '06 and earlier. I tried to get them for my '07 and the parts dept. told me all they show available is a generic black flat rubber flap with the Ford insignia on it. I believe the rubber flap is a universal flap.
I tried to put my molded '05 flaps on my '07 but the contour and wheel moldings are shaped differently. I'm sure you can still get the contoured flap for the older models as to why they ask the year and model.
I know you're looking for the Walmart flat type, but I got these molded mud guards from "Ford parts on line" or similar named website in early 2007. I believe they had Ford part numbers on them but it's been two years now. (Doesn't seem that long ago!)
I believe they fit all but the power running boards.