The equipment and supplies to build your own custom battery cables is available on Ebay, and for the cost of just a few good quality cables you can recoup your cost and make a few bucks on the side when somebody at a car show asks "Where did you get those nice cables?" All it takes is a hammer-operated crimping tool, a BFH, some bulk cable and the correct end terminals. I don't remember exactly what getting set up with all that cost, but good store-bought cables capable of cranking a 6 volt system efficiently ain't cheap! You can also custom-tailor cable length to your specific project needs.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!