Some of that is my fault. I confused ignition coil with starter coils. Jerry still has it, I don't. I got in the Medicare donut hole and didn't buy my medicine.
Martin: he did say he finally got 6V starter coils, so I guess the starter is 6V. I will wait to see why he converted back to 6V, if that is what he did.
Derek...you can run a 6V starter on a 12V battery/ignition system. I would seriously consider converting to 12V. But I really don't know what you have. I would ask that we don't talk about the starter coils anymore until I sleep one night.
Your issue is, as you know, is probably: bad battery, bad starter rebuild, timing or worse. Don't trust any of those. Ignition switch and wiring is also subject. The cable size and ground seems fine if bolted to a clean metal, major component.