Look at the switch on the starter. Does it have a side post? That post is used to get a 12 volt line to the coil just for starts. With the ballast resistor in line you might have too little voltage at the points when starting. The switch looks like this:
http://www.classicparts.com/1947-59-Starter-Switch-w_Side-Terminal/productinfo/53-712/#.VHtjCvldVmM
The side terminal is only hot when the starter is running. Simple wire to the + side of the coil and you should have no more issues.


Steve H