Challenger Drag Paks use a specific regulator unit which bears a sticker that reads: Challenger Drag Pkg. Car Door Module and displays part number P5MOPP319. Not visible are the marks left inside the door by the hand saw used to remove the adhesive-bonded inner door side impact brace tubes. This work was performed at Roush. Note the empty door speaker clearance hole. In true factory drag car tradition, these cars are strictly radio delete.