Check the voltage on each side of the fuses in the fuse box. A dozen years ago I was working on the factory AM radio in a '70 B-body and it would not make a sound. Come to find out, the fuse read 12v. on one side and 11.7v on the other. I changed the fuse and it read 12v on both sides and the radio came on immediately.
Another thing to check is what the stereo calls for in regards to 2 or 4 speakers and 4 or 8 ohm. However, this would probably affect the sound quality rather than no sound at all.