The 2008 4.7L is making nearly just as much as the HEMI when it debuted in 2003... Add a few bolt on's and it will be a well worth while transplant and a whole lot easier and stand toe to toe with most HEMI's...
So to answer the question, YES it can be done. There are a few Ram owners who have done this swap. You would need to swap the tone rings and step down to one plug...just leave the un-used spark plug in place or install a set screw in all the unused plug holes.
Most all the sensors on the later 4.7L can be used on the newer one.
You will need the throttle body adapter plates to install your cable throttle body to the "Fly By Wire" throttle body.
If you have any questions please feel free to contact me.