GX200 engine questions

Okay I have three perhaps four I would like to switch out. They are all gear reduced. The gear reductions are wet clutches and work well...engines are just worn out.

What I would like to know is...can I buy just a GX200 engine that will accept the reduction parts ?? Or, do I have to buy a whole new engine.

Also...are there after market clone that worth the saving $$ investing the time ???

Thanks...looking forward to hearing your come back.