Those rear fender wheel liners were standard (or at least really, really common) on the 4WD trucks (both my second gen 4x4's had them). So they shouldn't be to hard to come across in the salvage yard.
I like them, reason being is they keep rocks and road grime off the rear supplemental air bags mostly. They only install with those little plastic Christmas tree push pin things , so its not hard to install them, no downside to them as far as I can tell (not like they weigh very much or anything).
...