Did Shure publish a sound installation guide in the 1970s?
Yes. The Sound Installer's Guide was published in 1975, catalog number AL507. It is attached below as a PDF file.
Relative Loudness Levels of Common Sounds
dB to Voltage Ratio, dBM to dBV Conversion Factor
dB to Power Ratio
Microphone Power Rating, Voltage, and Impedance
Microphone Output Voltage, dB SPL, and Voltage Rating
Amplifier Output Power, Voltage, and Load Impedance, Power Formula
Constant Voltage 70.7 and 25 Volt Speaker Load, Power to Impedance
Measuring Input and Output Impedances, Formulas and Test Circuits
Speaker Line Resistance, Length, and Gauge
Power Available at Speaker after Line Loss
Balanced Low Impedance Attenuator
Audio Connector Wiring (3 Pin XLR and Phone Plug)
The Sound Installer's Guide supported the Shure SR (Sound Reinforcement) product line of mixers, power amps, crossovers, equalizers, and loudspeakers.