I knew about better exhaust scavenging due to even pulses, that's why I could see slightly better horsepower, probably torque as well. The even firing would keep the engine from rocking side to side but there are more second order vibrations I believe. Using a relatively heavy flywheel, something designed for a regular FE, could do the trick. The whole reason you have a flywheel is to smooth out the power delivery. The lighter crank would help with high rpm stability as well. You have to have a brand new crank made it seems these days for the FE anyways and yes, cams would need to be done as well.
I'm not sure if it would be right to get rid of the American burble from a SOHC though. There is something about the way our engines sound. And I've seen headers where they cross two primaries to even out the pulses, so if that was my only reason there is a cheaper way to pull it off. But that gets rid of that rumble sound.
