Complex sentence: The only special edition Manta ever produced for the U.S. market was the "Blue Max" in 1973, this amounted to a blue 1973 Luxus model, with a unique dark blue vinyl roof, mechanical sunroof, and automatic transmission.
Split into simpler sentences: The only special edition Manta ever produced for the U.S. market was the "Blue Max", in 1973. This amounted to a blue 1973 Luxus model, with a unique dark blue vinyl roof, mechanical sunroof, and automatic transmission.