When I needed a double eye cable from the switch to the frame, I ordered a custom length double eye cable from EBay so I could reach the pre-drilled hole in the frame for the original woven positive ground. I made measurements first using a piece of twine, added a few inches for slack, bends and stiffness, and ordered from an EBay site like this:
http://www.ebay.com/itm/1-0-Gauge-AW...DLy2tyzoqTzbLQ