Super Cabs are fine, I had one that I traded in for my Ex. Just be ready for a huge reduction of inside space
If it was me, I would be looking for a crew cab...
As for the 6.0, they can be a great engine, just be aware of what you are getting BEFORE pulling the trigger.
I know the 5.4 may be a little limited, but instead of getting a whole new rig, how about picking up a small trailer? You could use that to haul when needed, but have the Ex's space when hauling people or other precious cargo.
Good luck on what ever you choose