I've got the 3.5L.  You wouldn't run out of power with it.  What I'd worry about is having enough weight in front of what your pulling with a half ton.  Next trade for me may be a 2.7L as I don't tow a lot with this truck.  I imagine if you drive them all you'd find likes and dislikes from each brand but that 3.5L will flat out get with it.