For 1973, the fourth generation El Camino was introduced. Matching the Chevelle line and using the wagon chassis, it was the largest El Camino generation. Energy-absorbing hydraulic front bumper systems on these vehicles added more weight. There were two different trim levels of El Caminos during this period. The base model and SS option shared interior and exterior appointments with the Chevelle Malibu, while the El Camino Classic (introduced for 1974) shared its trim with the more upscale Chevelle Malibu Classic. The 307 2-barrel V8 with 115 hp (86 kW) was the base engine. Options included a 350 2-barrel V8 with 145 hp (108 kW), a 350 4-barrel V8 with 175 hp (130 kW), and a 454 4-barrel V8 with 245 hp (183 kW). Production of the fourth generation continued until 1977, when it was replaced by the Fifth Generation Chevrolet El Camino.