Your most likely going to have to use the standard dimensions as noted by
@Russell King and fabricate something. Unless you’re using a Quick Hitch with it, 3 points are pretty forgiving on precise dimensions so close is close enough.
I have a few Leinbach implements. They’ve been out of business for many years. They used to have a manufacturing facility in East Bend on Hwy 67 on the north side of the Yadkin River and a sales/repair place on Hwy 67 (Reynolda Rd) in the edge of Winston-Salem, about 15 miles apart. As I understood it (and could be wrong) one side of the Leinbach family ran the Winston operation and another side ran the manufacturing. The Winston operation shuttered first with the East Bend group shutting down a few years later.
Oddly enough I did see a website for Leinbach Implement but it was written like English was the author’s second language and anything past the home page went to some weird mess with that Chinese sort of pictograph writing. Suspect you’re on your own with that project.