I've done the retro Thunderbird thing. My little birds (55 & 57) values went up. The retro car causes a stir of interest. Many opted for the 02/05 Thunderbirds because it captured the coolness and similar styling without all the restoration/maintenence worries, but retro put focus on early birds none the less. Focus increases value.

New Challenger will stir interest in the originals moreso because the new Challenger is meant to be muscle in its heritage, moreso than nostalgia and image.

my opinion, of course.
Steve