Physical grounds have always been a problem. For the past 30 years or so, truck manufacturers have been running 2 wires to each light. International uses a stainless steel bolt through the firewall on their 9000 series. The bolt is first tightened to the firewall and then all the grounds are attached to it. We run a 4/0 from the batteries to the starter solenoid and another 4/0 from the batteries to the starter mounting. We run a 10 gauge wire from the alternator + to the starter and also ground the alternator to the starter. A strap goes from the starter to the common ground on the firewall. 40 years ago lights were a problem. Especially after truck manufacturers when from positive to negative ground. We now use Trucklite and a few Grote LED lights and stay away from cheap no-name LED and we have almost zero light problems. We use Trucklite grease on all plugs.

http://www.ryderfleetproducts.com/r...uct&gclid=COjO9KedscYCFQgtaQodKWQN3w

I don't even have a 67 or an 1157 bulb in the parts room any more.