Blinker issues
 

The blinkers on my 1970 c-20 are operating improperly. All my lights and blinkers operate as they should during daylight hours. The issue is,when I turn the running/head lights on and use either blinker the other blinker flickers. Front blinkers are fine. Does this sound like a ground issue? Does having a wood floor in the bed change ground? Any one else experience this? And ideas are welcomed. Thanks.

Re: Blinker issues
 

I haven't seen this, but bad grounds on old vehicles are common and show up in strange ways.
I'd ground the engine w/ the big ground cable, then the engine to the frame and ground body parts that have electric bits to the frame.
There's no need to use a big cable from the engine to the frame.
You may want to test with test leads and jumper cables. I have a long wire w/ alligator clips on both ends to do testing stuff. Maybe connect one jumper cable lead to the battery negative and frame, then a test lead from the tail light shell to the frame, then try to duplicate the problem.

I have degrees in electrical and electronic stuff and find vehicle wiring a pain in the butt. :) Good luck...