I don't think they existed back in the 60's
Or as you infer whether they exist at all.
These chords including the so called 'power chords' are as old as tertial harmony itself and have been in use for going on 500 years. Certainly long before '70's pop & rock' musicians think they invented them. These are not even true power chords if such a thing even exists. True power chords consist of just a root, a 5th and usually a second stacked root an octave higher.
Quote:
Theorists are divided on whether a power chord can be considered a chord in the traditional sense, with some requiring a 'chord' to contain a minimum of three degrees of the scale. When the same interval is found in traditional and classical music, it would not usually be called a "chord", and may be considered to be a dyad (separated by an interval ). However, the term is accepted as a pop and rock music term, most strongly associated with the overdriven electric guitar styles of hard rock , heavy metal , punk rock , and similar genres. The use of the term "power chord" has, to some extent, spilled over into the vocabulary of other instrumentalists, such as keyboard and synthesizer players.