4.7 H.o.
I was thinking about doing the same thing in my old Ram Charger. What stopped me, besides CLF Disease (Chronic Lack of Funds), was the fact that you can get a used 5.7 Hemi for only a few dollars more. Did not make sense to spend the money and time needed to make a 4.7 fit when other people have designed all of the stuff to make swapping a 5.7 Hemi easier.