No, I want a 4 cylinder engine. And that's, as you say, because of the regulations. The second regulation is cylindervolume. If I use the 2.3L from duratec I will race in another class than < 1999 ccm. But in other types (I don't know the word for it) of racing, there may not be the cylindervolume that divides the classes.
As you say, the V8 will be very heavy. And I need the car to be as light as possible.