Rear harness/rear lights not working

[cgster]

Been piecing my truck back together and have all of the front lights working but not the rear lights.
The rear brake lights, reverse lights and rear side marker lights are not working. Turning on headlights does nothing for the rear lights. The left and right blinker on the rear lights work. I have hooked up the ground wires for the marker lights but nothing. Any ideas what im missing? Also, this is for a 72 C10 Stepside. Thanks.