Anybody feel like discussing Old Mopar/Motorola hybrid AM radios?

I have never had any problems in 40 years from using 8 ohm speakers.
The output transistor's DC "source" is through the speaker. So if a higher impedance speaker is used, less current will flow and the transistor will be maybe a little less powerful, but sort of protected from harm by being operated more conservatively. The thing to avoid is a speaker of less than 3.2 ohms, which would cause excess current in the output transistor.

The "placir board" just seems like clever circuit board usage for the day, but many service men hadn't seen them yet in 1961.
So they gave that explanation.