No affiliation, but just found www.batterycablesusa.com
for 4 dollars I got a ground cable to replace my old one from the head to the coil mount. All automotive grade and custom built. Got it in 3 days. I probably should have gotten 8 gauge here instead of 6 but other than that a great match/replacement of the original for a fraction of the cost.

 

The thicker the cable the better in this case. You made the right choice going for a 6 gauge over an 8!

 

thanks! That's was also my logic, better on the bigger than smaller side for wiring