The fourth evolution of the Excalibur was known as the Series IV and was introduced for the 1980 model year. The Series IV received a new chassis that was 13 inches longer than its predecessor, but still available in a roadster or phaeton body style. A range of updates were featured on the Series IV as well as the first significant styling update in the cars production. The Series IV saw the Excalibur shift more towards an emulation of the Mercedes 540K instead of the Mercedes SSK, which had previously been the most similar aesthetic. Also new was the GM-sourced 5.0L (305ci) V8 engine that was exclusively paired to an automatic transmission to send drive to the rear wheels. Production of the Series IV Excalibur ended in 1984 when it was replaced by the Series V Excalibur.