Making your own cables is very do-able, if you know what you are doing. My only concern, and to be frank, is your basic question of what size cable is used. To start with, you should get a wiring diagram to plan your materials. If you make your own cable set, you will probably spend near $50 if you use good quality cable and especially high quality battery clamps. Besides the battery clamps, you will need connectors for the chassis ground, the starter, and for the alternator.
I'm with js12278 on this one. An OEM set is 'plug-and-play'. All cables are the right length, and have the correct 'connectors' on all the right ends.
Originally Posted by wj-jeepdrew
What size cables did you use? Id rather make my own than spend so much on the complete harness.