I think they may be all worth a try. When I mill them the ports are still no bigger than a Homey or Poulan 25cc. There is just somthing about the engine that is makes power. I suppose the twin ring helps. Plus they are ballanced so well. Very little vibration at all. All the toro's should make a good conversion. Some types may have a little more potential but I think they will all be good. I would like to see some numbers on an engine like yours. It may suprise you.