since no one else will take a new member serious in the chance that he/she is not some ubiquitous troll, i'll answer.
i've recently finished what you have suggested, everything except for a 'jake brake'. but with the discs, you won't need any other braking support.
... nv4500 2wd tranny (need the OD for highway speed and i believe the stock T-case is a divorced unit so a custom drive shaft and x member would be all i need) ...
it isn't that easy. you'll have to put the 'short' fixed yoke output from a GM NV4500 onto the rear of the Dodge NV4500, or use that style GM 4500 and change the input and clutch housing to the Dodge style.
however, you still won't have enough room to easily fit an intercooler in the engine compartment without interference from the headlight bucket/corner brackets. so you'll either have to
- run the Cummins without an intercooler and utilize the deuce radiator,
- use a ATW intercooler and mount remotely,
- or do what i did and get rid of the headlight buckets/corner brackets. this took a good bit of work and required making a subframe to hold the IC and rad, plus making new grill supports and using electric cooling fans.
also, the custom jack-shaft that you'll have to get made will not be cheap. you'll have to assemble a 'yoke-shaft' assembly using no less than 1410 parts.
use the title search function with '5.9 cummins' and you'll find my build thread. (man, i need to update that thing...)
it's easy to replace the MF with a CTD, but not easy to do if you want it to be a powerhouse.
oh, and i think the 100 mile jaunts are manageable, but i would get tired of it quickly. over that distance and i agree that this is not the vehicle for long trips.