Questions for Truck Hardware Universal HD Single Rear Wheel "L" Mud Flap Brackets

That bracket will do the trick for you

Here is the custom fit brackets for the 2014 F-350 with 21" wide flaps, https://www.sharptruck.com/truck-hardware-gb755553

The GB758053 would be the ones you want for the rear. The front flaps will fasten to the lip of the wheel well with the included self tapping screws