i reckon it might be a V8.. you probably could fit a Phantom's engine in there, but i dunno... im just guessing.
I believe the concept is equipped with a V-12 but if this were to see production, it would probably be motivated by a forced induction V-8.
which is dumb, in my opinion because it just makes the whole giant front of the sar look huuuge idk, i know its a style, but i just dont like wasted engine bay.
http://www.autoweek.com/files/specials/2006_geneva/castagna/sport/pages/01.htm according to the above link it is a V12