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BTW: My '53 Chevy (3100 truck) had a radio that must have been put in
later. It ran off a vibrator and reversed battery polarity did not matter
And it likely had a transformer output stage - not a power
transistor. It was an 'all tube" radio - most definitely- back in '53

If it was put in later, even if it had a vibrator it probably would not have
had a transistor in it. There were some car radios that worked iwth 12
volts on the plates of the tubes, except they could not make very much
audio power so a transistor or two were used in the audio output stage.