Just a side note, if it wasn't already mentioned, most LED lamps are polarity sensitive, meaning if installed the opposite way in the socket, they won't illuminate.
One more thing to try out, the intermediate harness (the four wire long harness that connects at the firewall and runs to the rear of the bed and attaches to your rear light harness, might be "Crispy" (weathered-dry rotted) and may be grounded somewhere along the chassis. I'd disconnect the harness at the rear tail light harness and probe the sockets for power when you turn on the flashers/turn signals etc...
Hope this helps!
Ben
Sorry, didn't see that you solved your issue.....
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