For the best result you should use a redundant grounding loop system, it's the best thing ever and you will love it. Your home has it.
It works like this, you run a ground wire with your other wiring, as you stop to ground it to the bucket or where ever you also pickup your redundant that goes back to the frame and then back to the battery, you choose a couple of points on the car to mount small junction boxes, you use a physical wire to connect everything back to the battery ground, it costs a few bucks more but its well worth it if you've had to chase a ground short or two, in your case you can use a connector and not even ground to the bucket, just take each bucket to a ground terminal and loop to the frame off the terminal and return the ground with a wire to the battery. About every five years it is good practice to run through the system and dress things up a bit. I will never build another car without this system. Think of an electrical system as a plumbing system, power is the water and grounds and neutrals are the waste, if you don't ground and neutral properly you don't get good flow out and you back up or dim.