Quoted:
To the OP: I'm sorry. I hope you like working on antiquated garbage. That engine is a dog, the 6.5L N/A and 6.5L Turbo are also dogs. I didn't feel the torque in those engines and they had a pissant amount of horsepower. It would be unsafe to drive on fast surface streets let alone fast freeways.
The Hummer H1 Alpha had a very nice powertrain (Duramax diesel) but they didn't sell them for too long. They looked at a new powertrain for the HMMWV but it was too costly from what I heard.
The 6.5L and 6.2L are not unsafe to drive on highways. They have enough grunt to be palatable, especially with the proper modifications. They won't be powerhouses like the 5.9L or 6.6L, but they aren't poor performers in Blazers and half-tons. Comparing a half-ton to a HMMV is apples to boulders comparison, there's easily a 5,000lbs weight difference between the two.
The 6.5L, with an upgraded turbo, some exhaust modifications, a PMD relocation, turned up IP and some bigger injectors will be somewhere around 450ft-lbs torque at a very usable RPM. The 6.2L with the Banks Sidewinder (with similar aforementioned modifications supporting it) is too palatable for a beater truck.