This is a small tidbit we got on it through a dealer email. From what Ive heard, they are supposed to be high demand for the extreme collector. Not sure how true that is, but we'll see. Anyway, heres the blurb we got from GM.
The Western Region has available some of the Anniversary 427 engines.
If you are not familiar with this specific motor and why it is so unique.
From GM Performance Parts, this is probably the most exciting new engine in years. It is the 427 Anniversary Aluminum Big Block Crate engine. This new engine is a modern version of the ZL-1 427 of the 1960ís era. We have built it with all new updated materials to offer an extreme 480 horsepower tribute to our heritage. Everyone who purchases these engines will be in a very exclusive club because only 427 of these engines will ever be produced and then this specific ZL1 tooling will be retired forever. Each Anniversary engine will include a document that will allow customers to receive a special commemorative owner's kit specifically assigned to their engine number.