For the next guy with this issue:
Home Depot sells a box wrench, 1 1/8" at one end and 1 1/2" at the other, and at least 18" long. The trick: it's not in the tool section, it's over by the trailer hitches. It's the right size for attaching the ball to the hitch. All of about $10. It did the job in short order.

A VW guy trying his hand at a '59 LB fs. Lots to learn, but it's about the journey.