Yep!
My dad worked at Flyer in the 80's and I remember him telling me that the spoiler was a space for the A/C.
Still, as a youngin', I always thought there was some kind of funny muffler in that spoiler that gave the D800's that "howl" in its sound that the other Flyers didn't have.
Of course, this was long before I knew about the difference in the transmissions and drivetrain layout - neither of which had anything to do with the spoiler but a lot to do with the sound.