I visited The factory in San Diego two year ago and this is what the engineers told me.
The unit will work with a diesel 350/450/550 but it is advised that you only use it in the OD mode unloaded. Putting a moderate or heavy load on the truck and engaging the GV O/D will result in shortened life and premature failure. The System was not designed for the harmonics and torque load that todays Pickup turck diesel produce.
The system is designed around a Volvo Penta cone clutch and yes they do install these things in a variety of hot rod cars, the difference is the harmonics and high torque loads that diesels produce. Diesels eat the cone clutch.
Gear Vendors does not trecommend trailer towning with the unit enganged.
Gear vendor does not recommend carrying heavy loads in the bed ( Slide-in Camper) with the unit engaged. They do say it will work just fine in a pickup as long you are in a unloaded condition.
Also their approach is a one size fits all, so the same OD unit that goes on a 32 roadster at 3200# will the unit they use on a F450 at 9900# empty. I was headed down this road until I visited the factory, at that time they told me they had no plans to update the unit or build a unit with better capacity.
This said I know there are folks out there that use the GV O/D, the one guy I know personnally used in a F350 2wd to tow a 12,000# fifth wheel it broke down after the third tow.
Hope this helps.
PS I have a GV OD in my 34 ford PU, but it is a toy and not used for work.