I've been listening to The Story Of Star Wars LP on headphones just now, and it's definitely got stereo effects on it. Much of the dialogue sounds pretty mono, though, while sound effects bounce around from ear to ear.
Also, I've noticed how difficult it is to notice the difference between Beru's "Luke... Luke!" line on the LP and the other version from the 35mm mix. Not as obviously different as her later lines, which aren't on the LP of course.
--SKot