I cheated a little, used a transformer to match the impedances. The CB "Speaker output" may or may not want to see an 8 ohm load, which would be a typical speaker impedance, so for most efficient power transfer, I put an audio transformer between the CB and the VIC-1 . The input winding is about 8 ohms and the output about 600 ohms, which matches the VIC-1 input impedance. Found a Stancor A-8101 transformer on ebay, but Radio Shack should have something similar. The transformer should be able to handle 3 to 4 watts or more.
The "Audio" input on the AM1780 has a higher input impedance and the signal is amplified within the unit, so this input is more suitable for CD players etc.
There is an article on this in MV Magazine issue 106, Dec '04......