LED signal light issues.

Hi I need help with this as well on a 1970 dart. I've replaced my front head and parking/turn lights to LED and it works. But when I replace the back lights the turn signal does not switch on. So far from reading this I need CEC Industries EF32RL or maybe the polarity in the socket is reversed? Also where does that relay go? I don't see it in this diagram.
Thanks


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