Ray it isn't peak hp that you look at for trans application, it is peak torque output which the 413 has in spades above the 5.9.We need @transman to chime in if he is around about the best way to modify one of the 46rh's to live in our application. No way am I spending 7k on a trans build. That said I am capable of building it myself so it will just be parts expense for me.
PATC sells kits if you're inclined - which one would be good to get experience chiming in.
https://transmissioncenter.net/product-category/dodge/?product-category=level-3-46re-46rh-518,level-2-47re-47rh-618,level-2-48re-dodge
None of those build shops have 46/47RH cores, so need to source a wreck.
