Its rated at 250 hp and 520 lb ft of torque. It will handle anything a comparable year dodge or ford will. None of the earlier diesels put up much of anything for hp numbers, the torque was and still is where its at, and 520 is enough.
Dad and brother both have d-maxes('04-05) range approaching 200k miles. Minor issues only. Dad had to replace stepper motors in dash gauges and both had to have the fuel filter housing rebuilt and that is pretty much it. They both run really good.
Fella I know had an '02 model he pulled a 10k plus grain trailer with it for 3 years and then traded it in on an '05 d-max because it didn't have lumbar support. Before he had the '02 d-max he pulled the same trailer with a GM 6.5...
It's hell eatin em live