Go with at least a 1g battery cable.
As long as the wire powering you ignition has power in both the crank and run positions, wire from "R" terminal is not needed. I would check first.bochnak said:
Yes it can, but would not cause slow cranking. usually it would cause a click or nothing from the starter. As wires get hotter, resistance goes up, anything to keep them cooler is better. If you are going to replace it, up the wire size to 10g.bochnak said: