You must be looking to keep the truck dead stock because your problem is easily fixable. Take a look at Thuren or Carli suspension for your solution to having the Cummins and off road ability too. If you are really brave you can be like a few of us and make your diesel even more reliable and fuel efficient as well. Just spend a little more time researching and see just how comfortable you are with the aftermarket. The options are very exciting and once you get comfortable with researching and getting the best parts on your truck.. you can truly make it exactly what you want. Whether it is an AEV Cummins with Carli suspension and an extra 100hp that gets 21mpg or a luxury land yacht that rides like a pillow while towing 20k+. My answer to your question is get the Cummins and turn it into your perfect rig.
ps. if we all were making decisions purely based on the money and what is logical financially then we would all have tradesman's with only the bare necessities. Buy what makes you happy to get out of bed and work to pay for it