Rear lights wiring harness

[i love my c-10]

Good Afternoon everyone!!

I bought a harness from Classic parts for the rear lights because the PO had a mess under there. It starts at the gas tank and gos back. Heres what I got. the left turn signal works fine. When I try the right turn signal the back up lights blink. the right light doesnt work at all. The bulb is fine. Already changed it. None of the rear lights work at night. and when I press the brake the left light and back up lights come on, still no right light. I have found that if it doesnt make sense then its a ground. So comes my next question. The harness has the sockets for the side marker lights and my truck doesnt have them and they have a ground. Is that the problem? Do i need to put bulbs in them or make jumpers? There is nothing in them now.