!!! Check here: http://elcaminocentral.com/
they have tons of info. Might as well sign up while you're there.
Beginning in '74 the SS was just a trim package but there are lots of goodies available for the 5th Gen El Camino's as they are very popular so making it a bit more than just an SS in name only is pretty easy. Plus that same body was in production from 1978 through 1988.