From what I understand the soft Yanmar
rubber mounts were to help with the idle vibration but were limited in the high load where there is no shaft thrust bearing. The poly mounts are better with oils & thrust. There is not a lot of cost difference. Yes the Australian one will drop straight in. They are made locally to me but as yet I have not changed to them. Seen them at boat shows etc & would change to them if mounts are needed.