I upgraded from a 1/2T chevy to a dodge 3/4T. Night and day difference but i'm sure you realize that through your research.
Just for reference, on my Hawk, I have about 1.5" of clearance above the roof. Its pretty tight but I think it looks sharp. I'm not a fan of huge gaps between the roof and cab. There doesn't seem to be much wind buffetting. On the rear opening of the tailgate has about 3/4" of gap, its a tight fit. The top of the box rails is also super tight, there is about 1/4" from the top of my rails to the bottom of the camper. I do have stupid little plastic caps on the box rails, so that might account for some gap. Its a super tight fit and does take some more wiggling to get on but it looks really sharp as it looks likes its built for the dodge.
oh, I should also add, my box is 6'3", so there is 3" of camper overhang out the back