What all will fit?

Is getting a 5.9 in the output that we're looking for, and to play nice with the existing accessories, going to be cheaper/easier than dropping in a 5.7 and making that work?
I know the 5.9 was available in both a Dakota and Durango of this generation. My thought was to basically do a 5.9 swap, but with more HP/TQ. I'll post the trans that she's got later this evening. The original owner actually kept the window sticker.