Check the main cab ground point as well, all the light grounds go through it. Location: driver's side kick panel.

Should be a threaded hole for the factory ground strap on the passenger side. On my '85 there is the battery ground to the fender. Then from there to a bolt on the frame and from there up to a bolt on the side of the motor mount bracket on the engine. Also back of the head to the firewall. I upgraded all the ground connections with some 1/0 welding cable on my '85.