Complex sentence: The first XJ-S appeared in 1975 as a 1976 model after first starting in the late 1960s as project XJ27 with initial shape set my Malcolm Sayer but after his death in 1970 was completed by the in house Jaguar design team headed by Doug Thorpe.
Split into simpler sentences: The first XJ-S appeared in 1975 as a 1976 model. The development of the car had begun in the late 1960s as project XJ27, with an initial shape set by Malcolm Sayer, but after his death in 1970 it was completed by the in-house Jaguar design team, headed by Doug Thorpe.