One story that make sense, is this car was like a test car Chrysler had way back to test the 1967 model. Than car was updated for the ´68 model. Suppose this was done maybe summer of ´67 for the ´68 production cars. This car was now just sitting and available for the Hemi A-Body program team to start working on. The Mule had fiberglass fenders, but the side markers were later deleted to save money and time.
As for the fenders, body was shipped to Hurst with steel fenders on. Car was a roller at this stage, and in order to get the grill and stuff with the car, this is how they were delivered.