[Carl n Susan]

Since the pinbox normally clears the naked side rails, I am guess you have a tonneau cover of some type. Are the rails for the cover what are hitting the pinbox?

In either event, a few of us have trimmed off the back edge of the pinbox. I believe you can make a 45° cut starting about 2" from the rear of the pinbox and create enough clearance. This won't affect the load capacity of the hitch. Someone posted pictures before. You might try to find them with the Search tool