Lots of opinions but just as many misconceptions.
The first gen Camaro had several purpose built combinations.
The RS was always an appearance package. The SS was always a sport package unrestrained by any racing class rules (the Street Performance choice). The Z/28 had only one purpose - it was designed, built and sold to homolgate the Camaro race car into the SCCA Stock Road Race class where the Boss 302 Mustang competed in AND beat the crap out of them. Win that race on Sunday and sell Camaros on Monday. Z/28's were supposed to be sold as a "production vehicle" to anyone who walked into a Chevy dealer and layed down the cash. It was not supposed to be the top dog Camaro, it was supposed to be the
Top Dog SCCA Production Car in the 5.0 liter SCCA Production Car racing class. It had no street domination intent. The SS and above were designed for street domination where engine size was not limited by any rules restrictions.
This changed somewhat with the second generation Camaro. The SCCA rules were changed to allow anyone to de-stroke a production engine to race in a different displacement class and still be considered a "production" car. Racers could purchase a stock 350 engine equipped Camaro and race in SCCA 5.0 liter classes by installing a short stroke crank to get under the 5.0 Liter max engine size limit. GM no longer "needed" to build factory 302 Camaros to homolgate them as production vehicles so they discontinued the 302 engines for '70 and sold showroom Z/28's with LT-1 350 engines.
The SS could get a you a 350 or a 396 if your wallet held out. You could go as fast as you could afford with the SS, COPO and Zl-1's. Those could be considered "Top Dogs" for the street.
GM made a Z/28 after 1969 but they were never as close to being a pure, purpose built race car after that.
The SCCA competition died out but the legend lives on!!
-Mark.