Marc
Some FC engines do have cassette transmissions and rotary valves but not all (and not legal in the CSC). However, in the case of the Pavesi, the FC head, carb (manifold and reed cage) and pipe bolt directly to the ICC engine. In fact, those are the only differences. In that form, the engine produces close to 55 hp. Such a combination will waste the motos easily.
Just putting a big carb on a standard ICC, actually may hurt performance. With the standard ICC pipe and head configuration, you end up with too much air (slower air speed at the carb venturi) and it actually reduces power. So unless they change the pipe and head, they could actually get more power staying with the standard ICC componets and work more on tuning.