Left turn equals both tail lights flashing???

[HSRACER]

So I just got a new to me 69 gmc and I was inspecting the lights before driving it home. Everything works properly until I put the left turn signal on. The front flashes fine but in the rear both sides are flashing. Right turn works properly with only the right side flashing in the rear.

I pulled the connection at the rear and found both lower pronged had flashing power to them which means that the problem is up stream of the actual tail lights and rear wiring harness. The factory leads along the frame are all ther and connected and the plugs at the firewall is solid and correct. It then seame to go to the steering column and the lower connection point which I thought was neutral safety switch?

Any advice of what to check next is appreciated!

[HSRACER]

Sorry, posted twice by accident!