Fantasy football trade question?

I need a WR I have C Johnson, and then I am in trouble I have Chambers, Hestler, Bobby Wade and Joe Horn. I am pretty deep in RB. I have Rudi Johnson, Frank Gore, Willis Mc Gahee, Cedric Benson and Chester Taylor. What running backs could I trade to pick up another top WR. I would like M Harrison, Steve Smith, TO, or Holt. but would consider a second level reciver