all the 6.7 engines have an exhaust brake.
You can get the wide track axle on some of the years prior to 2017, for example my 2016 has the heavy tow package which gives it the wide track axle and 4:30 gears. 2016 350drw and f450 both had 14k gvwr but the 450 does come with 19.5" wheels and a step up in rear axle size.
2017 they stopped this , you can no longer get the 4:30 gears or wide track front axle in the 350drw. Maybe ford realized this model was cutting into 450 sales?
There are still a couple 2016 f350 drw with heavy tow sitting on dealer lots.