I've included a photo of the rough dimensions of the mounting bolt pattern. If I've misunderstood, let me know and I'll get the measurements you were after.
I think you are right to stick with the Greenies. It suits me better, even if I do need to do a bit of work. They all need some work, even from new. My brother in law's new Cub cadet RZT S series is already throwing belts before its first service (albeit overdue- could be entirely their fault).
I should pick up my new old Greenfield in the next week, and hope for at least a few hours of trouble-free cutting.
The scientist in me wants to find the best glue on the market for metals and put the old engine back together (for fun only) to see how many seconds it runs for before throwing the governor away again. Reality will prevail though. It will sit in the shed for far too long before being offered as parts. I suppose this forum would be a good place to make that offering, when the time is right.