NY will be a bear to get it legal. In TX we can re-title it as a diesel as long as its not newer than a certain year. But in CA it was a big no-no on anything that wasn't exempt (76 or newer)
I also suggest the 4BT over the 6BT or ISB. Just so I don't lose you... 4BT is the 4-cyl, 3.9L version of the 5.9L. 6BT or 12-valve describes the 5.9L up until about 1998. It was mechncially injected, so no chip, tuning is as easy as using a screwdriver. Then after it became 24-valve and computer controlled, also known as the ISB in industrial applications. Usually in dodge circles they're just referred to as 12v and 24v.
A 4BT is a turbo swap and some mechanical tuning away from 300 hp/500 tq, and in many tunes will return 25-30 mpg depending on how the rest of the truck is setup.
Also, most of the upgrades to power production in a diesel have to do with increasing its efficiency by altering injection timing and additional turbo pressure. More cylinder pressure means more BTUs are released from the available fuel, which not only means more power but also less fuel is required to achieve the same driving style. Kinda like increasing static compression ratio in gas engines.
The 6BT weighs in at about 1100-1200 lbs, while the 4BT is about 750-800, which isn't much more than a big block mopar. I also know that it sounds impossible, but in a 1/2 ton frame, you'll twist it like a pretzel with a 5.9. Weight + low end torque = ripped motor mounts. Its almost as if diesel torque is stronger than gas torque... even though I know it isn't.
Your Dodge probably also has a D40 rear. A hopped up 5.9 is strictly D70 or 11.5AAR territory. A hopped up 3.9L can be handled with a D60, 10.5" GM FF, or Sterling Ford 10.25".
