[warthog5]

There is a free shareware program called WireSizer 2.0 and it is excelent.

To deturmine your batt cable size you will need a amprobe.
Clamp it around your battery cable and spin your motor before you tear it apart to find out how many amp's the starter draw's.
Starter draw imfo is not easy to find in any manual's.
Then when you move your batteries you have that imfo to inject into the fourmla.