Hughes Cam in Magnum - who has one?
I have no experience with the cam, but as a general rule, when you increase duration, the power band moves up the rpm scale.
That said, I would think that the low rpm torque is going to be somewhat less then the stock cam.....
For that reason in my ongoing project of putting a carbed 5.9 in my dakota, I stayed with the stock cam, at least for now.
Good luck, and let us know how it goes.