You might want to contact Iron Man Andy. He was doing a D30/D44 hybrid. Basically he was welding D44 Cs on and using D44 knuckles. If you were doing that, using the ones with a spindle and hubs would give you an awesome combo that would stand up to what you have in mind. But I think that trying to make a unit bearing stand up to 38s is marginal at best. The D44 knuckles and spindles will take a real beating on a heavier rig and stand up to it nicely. Ask me how I know.