The fifth and final generation El Caminos were built from 1978 to 1987. They were down-sized from the previous generation. This final generation lasted far longer than any other (10 years production). The El Camino remained popular enough that it even outlasted the Chevelle/Malibu line by several years.
The El Camino now had two basic models. The Classic (standard) model, and once agian, an SS model. The Conquista was an option package on the standard model. The "Royal Knight" was an option on the SS and featured special graphics.
The GMC Sprint was deleted in 1978, and was replaced by the "Caballero". The Caballero also had two basic models, the Standard, and the "Diablo". The Standard model could be ordered with a "Laredo" trim package, making it equivalent to the El Camino Conquista. The Diablo was similar to the El Camino Royal Knight. In 1981, the name of the "Laredo" package was renamed to be the "Amarillo" package.
In 1982, the El Camino and Caballero went from having two headlights to having four.
It appears that 1978 was the only year that a fifth-generation El Camino could be orderd with a 350 V8 and a 4-speed manual combination. Diesel powered El Caminos and Caballeros were built in 1982, 1983, and 1984. They were not very popular with the public.
In the latter years, a special model called the "Choo-Choo Custom" was built on the El Camino SS. It featured a "Laguna" style front end and special body equipment. It was built by a firm outside GM, but it could be ordered through any Chevrolet dealer.
There was also an "IROC" El Camino edition, featuring the same "Laguna" front end as the Choo-Choo Customs edition. More research is needed on the IROC version.