There's a 1977 M20J for sale on controller that has a very good price, but one thing in the pictures jumped out at me. It looks like it has a two-piece windshield, which I did not think ever was available on the J model. The pictures aren't the highest resolution so it's hard to tell for sure. It may also just be a strange reflection or view of the support beam above the panel.
Does anyone know if the two-piece windshield was installed by the factory on the earliest Js?