It would be a massive undertaking, a 5.7 hemi is a much easier upgrade and more rewarding when done.

To do the 5.9 you need the older controler that will not comunicate with the rest of the truck, you need a new harness because it don't plug in and you need a new trans as they function very differently.

The 5.7 on the other hand can use the existing trans, computer, harness with some mild mods, and a few other little changes.