Your new radio has an electronic tuner, doesn't it? How many wires per speaker does it have? Does it have one or two each? Your coach should have two wires per speaker.
Your new radio, if it has electronic tuner and clock (it should), will have two wires for power, you will need to connect both of them to power (probably the black wire, but check it with a test light to be sure) so it will retain its memory functions. The white wire should be ground, you will need to connect this, since the radio is probably inside the plastic end cap. Plastic is not a good conductor of electricity.