1979 Other Chevrolet Models parking lights

Electrical problem
1979 Other Chevrolet Models V8 Four Wheel Drive Automatic

I have a 79 chevy 3/4 ton pick up. My break lights were out and I replaced the fuse. The break lights work now, but I have no tailights when the headlights are on. I have running or parking lights and headlights but no taillights. The turn signals also work. Are the rear lights on a different fuse then the brake lights? I could not locate any fuse for them.