JT. I found the image on the internet. I was trying to help you identify the issue you are having.
That hatch looks like one made by the manufacturer. Was a common thing during the year your boat was built. The builder had all the materials to make a fiberglass hatch and so did.
You can repeat the process or you can upgrade and put in a modern designed Lewmar. They cost bucks not your time. They are a significant upgrade.
Or you can choose to go old school and build yourself a wood framed hatch to fit the hole and put say plexiglass over the top to give you a skylight in the boat.