Can this be duplicated with a 5.9 build??

You can build a stock short block 5.9 magnum that will make 400 ft lbs from 2500 to about 4000 easy as falling out of bed. Insert a mild cam and go.

Yup, and hook it to an overdrive trans with the right gearing, that'll tow nicely. I considered that option for my '72 D200 which currently has the original 360 2-bbl with a 4-bbl and headers. It towed my Duster on a U-haul trailer (5000 lbs?) and it did OK but going up some of the hills on I-25 along the Front Range of CO was a bit of a struggle. I decided on building a 440 because the truck currently only gets 10 MPG unloaded anyway (strangely doesn't change much when towing) and the torque will hopefully be on par with the V-10 although likely not peaking at quite as low an RPM. And I can keep it simple with a 727 and 3.55s with 32.5" tires. Chrysler designed the iron V-10 specifically for truck use in place of the Cummins diesel, it was mated to the same transmissions and running gear in most cases. I'd love to have one some day, but then I want a Cummins too lol