Buying park with small lots

The park is in Michigan that I have under contract for 375k with 50k down, The lots are 50-60 ft, what I am wondering is who do I contact about moving in bigger homes, I called the local city hall that the park is in and they had no information to give only to tell me that MH parks are state certified. So do I call them? What branch do would I call to find out what hoops I have to jump through.
Also the park is grandfathered in and not up to code so is the state going to make me bring the park up to code to be able to bring in new homes?

There should be a zoning, planning & development, or code enforcement department with your city that can help. For smaller cities with like 10K population or less you might just need to speak with the City Manager to get in touch with the right person. In some cases they just don’t have formalized zoning and you should be in a position to document this as best as possible through your dealings. Good luck.