Complex sentence: The final year for the mid-sized Le Mans was 1981, the station wagon dropped and only the base and Grand Le Mans models offered initially and joined at mid-year by a new LJ trim level positioned between the base and Grand models.
Split into simpler sentences: The final year for the mid-sized Le Mans was 1981 with only base and Grand Le Mans models offered initially. They were joined mid-year by a new LJ trim level positioned between the base and Grand models.