Normally SIZE and WEIGHT has been the enemy of converting a Murena (or any other car for that matter) to more than a 4-pot engine.
The Alfa V6 is a very tight squeeze, and this is also why some consider the VW VR6 as the only real candidate if any space should be left free.
However, now there is another - and this is even a V12 ! :
http://www.gizmag.com/spanish-engineer-crafts-the-worlds-smallest-v-12-engine/20636/Alright, its until now only powered by compressed air, but that's environmentally friendly too, ...
any takers ? :-)
/Lennart