The "other" motor you might be refering to would br a 6.4 liter...not a 6.3. Thats going in several other vehicles.

No one will know for absolutely sure until it comes out but all evidence lately...including these pics and several others sais 427.

Project "blue Devil" is a twin turbo car..Jay Leno already has a working prototype of this motor from GM and its hitting over 1000 hp.

Its funny because that entire article is now removed. If it were not true I believe Corvette Magazine would have replaced it with a "correction" to the info posted. They didnt and removed it completely and replaced it with an old article. Obviously this wasnt meant to get out yet. Only time will tell...but I am thinking its a 427.