Before July 4, the Clinton administration plans to ask Congress to set aside as wilderness 5 million acres of land that now lie within 17 national parks, prohibiting new development and roads. The biggest single change under the plan would give wilderness protection to more than 90 percent Yellowstone National Park’s 2.2 million acres, as well as much of Glacier National Park in Montana and Big Bend in Texas. But Congress has repeatedly rejected proposals to give wilderness status to national park land in the Lower 48 states, and Republican leaders aren’t likely to be enthusiastic about this plan.