I converted one, but I never posted the project. I built and A-frame adapter. I had a solid bar on the bottom of the A-frame that the bottom 2 points of the tiller attached to. Then I had a removable bar higher up on the A-frame that would slide through the holes on the lift arms of the tiller. On the outside of the A-frame I put pins in the right places to accept the 3 point hitch for my tractor.
I never cut or welded a thing on the tiller. The A-frame adapter was completely removable.