...just plan are your moves an execute. should take 3-4 weekends to complete a swap another couple to wrap up...
This statement should be qualified, I'm doing a 6BT in a square body crew cab that's being turned into a CUCV, I have about year into the truck and I'm still getting parts collected. Expect to spend around $5-10K putting a 6BT in "correctly". The time it takes depends on what level of technical expertise you or your available friends have, the tools and space you or they have, and the time you have available for working on the project. It's funny how missing one important part in the middle of an assembly can stop it dead in its tracks leaving you waiting for the UPS guy to deliver your part from where ever you can find it. If you are on a time crunch, like if this is your daily driver, I'd recommend having all parts of the assembly mocked up and complete before even starting to tear down the original drive-train. This lowers the risk of the project tremendously.
For my truck, I already have a daily driver pickup which doubles as a parts runner - it would suck to tear down your only running truck only to find you need a part which requires a truck to fetch.
Other than than my opinion having driven trucks with both engines, the Cummins 6BT is the better engine, the transmission that Chrysler/Dodge put behind the Cummins is a weak point - the web is filled with stories of people chewing the NV4500/NV5700 up by driving "spirited". The nice thing about the Cummins is that is is a wide install-base engine - everything from agricultural and construction equipment, generators and water pumps, to on-road trucks school buses and marine applications - so there are pars options out there that even the local Dodge dealer won't think of, even 24Volt parts if you want to keep the original CUCV dual voltage system. There is no cast-in flywheel housing, so you can unbolt the flywheel housing and buy one that fits the transmission you like after the fact. Being an even cylinder count inline engine, it's much easier to balance, since you only have to match the piston and push-rod weights and balance out the crank shaft separately rather than getting complicated with the crank shaft balance as an assembly with flyweights. The only thing it lacks for my definition of "perfection" is replaceable cylinder liners. There are Dodge trucks out there that have put over 1-million miles on the original block, I haven't heard of and definitely haven't seen personally any 6.2L or 6.5L GM diesels with more than 300K, without major engine repairs.
With the P7100, the big risk is fuel starvation, so even if you trust the maintenance of the engine source, replace your lift pump and fuel filter. With a pre-97 block you may also have risk of the
Killer-Dowel-Pin failure, so take a look inside the gear-train cover before you spend any time fitting that block in the truck.