69 Valiant Radio Help

Get a test light. If the red wire for the factory radio isn't hot with the switch in run, you probably have blown a fuse. And yes the yellow wire goes to a 12 volt source . Thats for the radio memory and hot at all times.
i really dont care about Kenwood model number manual yada yada, these 3 wire colors and connections are pretty much ISO standard connections for DIN applications.