Shower knob problems?

Years ago my grandpa made a homemade shower in their basement. Pipes come down from the ceiling a curved pipe is where the water comes out. two knobs that connect directly to the pipes control the hot and cold water. we want to fix this up. were gonna put a wall 6 inches from the wall that the pipes are connected. once we put that up how would we move the knobs that control the hot and cold water without moving the pipes. someone said you would have to get long shower knobs what kind and how would you do this, does anyone have any charts or pictures, instructions?