The main distinguishing features of this engine were a slightly different camshaft profile from the standard ultra high compression engine and factory dual exhaust. (en.m.wikipedia.org)
When Charles F. «Boss» Kettering developed fuels that would allow higher compression engines to operate without knocking, it was to maximize fuel efficiency in the face of a gasoline shortage, not to herald the beginning of the muscle car era. (bestride.com)
Conversely, some higher compression engines can downtune in order to cope with low octane petrol... some can't. (mechanics.stackexchange.com)