Nice article in a recent RoadRacingWorld issue about a fellow who stuck an air-cooled 796 Monster engine in an 848 (kept it all stock, I think). Probably cheaper than modding the S2R in the long run.
Wasnt there someone who slapped on desmosedici style fairings on a 796 too? that seems even easier... weld in some tabs to hold the body work and there you go.