I don't think you can. I am looking at my RS4-2 and the layout of the RS4-3 which is shaft driven and the layout looks completely different. If it is possible Mike please explain.
On the RS4, the engine is transverse, on the RS4-3 it's longitudinal. And there is a huge difference in chassis design to accomodate all the new shaft drive parts. I think it's a no-can-do.