A group of south Dallas community leaders are objecting to plans by the city of Dallas and the Texas Department of Transportation to convert the S.M Wright Freeway into a six-lane boulevard.    The Unify South Dallas steering committee wants the freeway to become a four lane road with commercial and residential development on either side.  The committee met Saturday, and says TXDOT wants to use South Dallas as a pass-through, while it wants to give the neighborhoods a street to develop around.  TXDOT’s engineers have said the problem is a four lane road simply can’t carry the number of cars that will use it.