I saw this thread last night and after looking at the sticker for the $160k Blackwing, I did some digging myself to see what could possibly be included in the $36k 20th anniversary package. I couldn't find much but I did find this article from this past August:
The V cars look mean in black.
carbuzz.com
"Aside from the color, which will not be unique to the anniversary cars, the package also adds a custom grille header, wake-up animation screen, and unique puddle lamp projectors. If we're being completely honest, that's not a ton of equipment, so the cost of this package shouldn't be too much higher than the paint."
GM: Hold my beer