The mounting plate and flywheel on the SA200 w/Cont engine will not interchange with the Kubota. We had a customer who coupled the two together with a little machine shop work to make the bolt patterns match. It ran a couple of days until the torque of the engine snapped the main armature shaft off just behind the windings.
To be honest Tom Fowler of Hybriweld is the only one to properly engineer putting a Yanmar on the SA200's. Don't think our shop hasn't tried combining the Perkins or Kubota on the SA200's. We just aren't confident with their prolonged operation.
Good Luck