The way I wired my rail it doesn't use the frame as a ground. It has a cable that runs back to the battery from the grounding locations.....I use a #2 from the battery to the engine block, a #2 from the battery to a grounding point in the electrical box and then a #10 up to the front of the car for the gauges and switches. Basically everything has its own grounding path back to the battery.
I did it this way because I didnt want to scrap off the powder coating plus it eleminates the potential of a bad ground using your radiator or engine as a path for return.
And of course I did check the ground points for proper torque and contact.
