JD 325 garden tractor needs a new engine

Hi, I've a JD 325 garden tractor with a 18hp kawasaki v-twin eng, and it needs a new one.I was hoping you all here could advise me which engine would be the best replacement for this one since they no longer make the engine that originally came with this garden tractor(bummer)? I'm new and I'm not sure if this is even the right place to post this question, all help is greatly appreciated!

Thank you in advance,
Randall