IMDb claims the producers had real heather imported from England to make the California landscape used in the film make more like authentic "Brontëesque" moors. I don't know if it's true, but it does sound like one of those romantically outlandish Old Hollywood-tidbits of information.
In a departure from the novel, there is an afterlife scene in which we see Heathcliff and Cathy walking hand in hand, visiting their favorite place, Penistone Crag. Wyler hated the scene and didn't want to do it but Samuel Goldwyn vetoed him on that score. Goldwyn subsequently claimed, "I made "Wuthering Heights", Wyler only directed it."
Cathy: Heathcliff, make the world stop right here. Make everything stop and stand still and never move again. Make the moors never change and you and I never change.
Heathcliff: The moors and I will never change. Don't you, Cathy.
Cathy: I can't. I can't. No matter what I ever do or say, Heathcliff, this is me now; standing on this hill with you. This is me forever.