Rear valance

The original Boss 429 rear valances did not have cut outs on them for exhaust like the 428 Cobra Jet cars had on them.  At some point in its life the Lawman rear valance was replaced and the wrong one was put back on.  See photos below as the car was, and how it looks today.  

Part of the reason for that it seems that when the Lawman was run on the tracks and for demos in 1970 they removed the rear valance.  When looking at the original videos you can see that there is no valance mounted.  This could have been for air flow since the radiator is mounted in the trunk area and the fuel tank is in the front of the car.  Then at some point the wrong valance was put back on.