There was another thread on this topic a few days ago. Yes, they can stop you from replacing any old homes in parks; even "gradfathered" parks if the local government wants no more parks. This is how they kill older parks. It can backfire, however.
After Hurricane Ike, some small towns said the homes couldn't be replaced so instead the owners patched up some of the worst looking homes you'd ever seen. Legal, yes. It's called the law of unintended consequences and law makers do this all the time trying to regulate businesses they don't understand. If they allowed new windstorm approved manufactured homes to replace the old ones the tax basis would go some $60 - $100k on each home. Instead they have worthless, patched, barely livable trailers, complete eyesores.
You need to call your local building permit office and see what their requirements are for homes. Do it anonymously and don't tell them the name of the property, just ask general questions and you will quickly get a feel for how they regard Parks.