I've thought about gettin the stepside wheel wells and makin em work too. Funny that someone mentioned the rubber flaps...they're actually available from GM for the front of the rear wheel well...there's a TSB about it. Turns out that the General attributed premanture rear brake pad wear to water, salt, and other debris, etc. getting on the rear brake assemblies, and came up with these mud flaps for the cure.

 

cool, wish it would cover the whole well, but still a start, I have a pile of mud buildup on my rear bumer currenlty, that and 6" of snow too...