[bhill86]

I can’t say for sure but doubt you can fit the later radio in the earlier dash. Otherwise why would GM redesign the dash? The bezels are certainly different. It may be possible with cutting. Could it be possible what was installed in your dad’s car was aftermarket?

As for the speakers 77 got one rear only. Never two from the factory.

I’lm not overly familiar with the GM CB option of 77 but based on radio/8track wiring I’m familiar with I don’t believe CB audio came through radio speakers