Thanks for the tag Fred.
As you point out, there are no US Truck specific workshops.
Almost all of the work done on mine has been done by Machinehead 4x4 - although actually the suspension was done by Titan Performance. They changed my upper arms when fitting the Kings.
In this case however, I would approach Rami Automotive, they are most likely going to be the easiest option. They know ‘American vehicles’ well, albeit it Jeeps mainly. But they were helpful with the f150 also.