Question On Replacement Kawasaki Engine?

I have a older Scag Belt Driven 36inch Walk behind and i need to get a new replacement engine. The model engine i have is a FH451-VAS09. This engine is discontinued due to environmental issues. Does anyone have any suggestions on which model i should go with or that would mount up correctly to my mower. I want to stay with Kawasaki Engine just need a replacement in the 15-19hp rating.

Thanks Any help would be appreciated.