Black 1971 front and rear rubber bumpers are not shown as being available in the 2 different print edition 71 books that I have.
They were available in black in 1970, shown in those books as pn 2962381 front....2962396 rear, called black velvet.
Perhaps they used a black 1970 style bumper on the front of the 71 like they did in this press release 1971 Cuda photo.