another potential thing to check...

I once had a problem with the wiring from ignition to coil via resistor that had me cranking like you are. To rule this out put a hot wire from + on battery to + on coil, preferably with an alligator clip (so you can unclip easily to shut engine off if it starts). Don't leave hot wire connected or run car for extended periods like this as coil will be getting more/constant volts than its built for.