Love those fullsize 250+ Fords.
You can improve the ride a lot with moderate improvements. Carli is nice, but a bit overkill sometimes. BDS 4 link, 4", with custom 2.5" King shocks from Accutune or Filthy Motorsports can do very nicely. But feel free to run BDS's Fox shocks for a bit before committing to thousand dollar shocks. I prefer the BDS four link over the radius arm option, because the 4link has a new mounting bracket that keeps the arms a bit lower, more level. I have no idea which has more clearance, but I'm sure the Radius arm kit has plenty.
Remember, you need to drastically stiffen your damping to get these trucks to ride well. Then lower your spring rates if possible for better ride over slow speed bumps.
Fox ATS is the best steering damper on the 17+ trucks. Not sure about the earlier generation. I know that King also has a good damper.
37x12.5" Cooper STT's on a 18" +20mm offset wheel will ride very nice. 20" wheels are the debil. We'd be doing every fullsize overlander a huge favor if we stole their 20+ inch wheels and tossed them in a lake. Avoid negative offset wheels as well. End up looking like a roller skate chebby with those.
I think the coil over kit costs you a little bit of travel on the big Fords, with no payback other the ride height adjustment. I plan on sticking with a more standard 4" spring and OEM shock location. I'd reconsider a coil over kit if someone could prove that they cost no travel compared to having the shock next to the coils. Because having a King 3.0 inside the coil, and a 2.5 next to it in the OEM location, could be hot.
Sadly, really cool bypass shocks serve no purpose on stockish Superduties.
Then later on, if you feel ok about reducing payload capacity, you can try Carli's Deaver springs. BDS's front springs ride fine. With the right shocks and springs, the BDS kit can be as nice as Carli. But Carli gets you darn close to perfect, out of the box, every time.
Eventually I want my truck to look like this with Method NV HD wheels +20mm offset, but by using BDS parts. Carli has no gasoline truck kits.: