I just never understood that MB would not have a direct ground cable to the engine block. Grounding to a single fender can't be good for long term.

With that in mind, I found a wide open area at the bell housing. I wanted to use the bolt lower that didn't have a bracket, but it was too close to the exhaust pipe. So here is where I decided:



There are several ways to connect to battery but I choose the easiest. There is an empty stud on the batter terminal.



I decided to go with a #4 wire that is 40" long. The common part number is A40-4L.



To remove the bolt from the bell housing use an E14 socket.



Slide the terminal on and retighten.



After threading the cable around the RCM box, you can then connect to the battery using the appropriate nuts and washers.





I slid some loom on it just for additional protection.