http://www.datasheetcatalog.org/datasheet/sanyo/ds_pdf_e/LA4555.pdf
Have not found a Drake schematic, but typically, radio manufacturers
use the same values spec'd out in the chip manufacturers datasheet.
The circuit used is probably one of the bridge configurations shown
since stereo would not be needed.
As you can see, if either of the output capacitors opens up (C7 or
C8), you lose the output. You should be able to trace down the caps
easily since one side of each should be connected to the speaker.
Jim