Well we dont have to be engineers to understand the basics of how the ign coil works. I am no engineer but I was taught some about the counterelectromotive force in the ign coil primary windings and that the normal ratio of primary and secondary windings with points was about 100 to 1 and transisterized ign coils average about 275 to 1. And I am sure we all know about coil magnetic field buildup (saturation) but most of that is not what the original poster asked. We just got a little carried away when he asked about what resistance ballast should he run. I guess when I look at a performance coil you have to figure what can change to cause more output ? The ratio of the primary and secondary windings or the amount of current flow in the primary windings to a point.
I would agree about what was said that the Super coil is designed for most of the primary resistance to be external. I know when I bought one many years ago it came with a .25 ballast and I will say if I was running points I would not run the full 12 volts to the coil like I am doing now with the MP electronic ign. Since the ECU can control coil buildup and current flow I would think thats why I have been able to run the full 12 volts to the Super Coil and have no problems with no external resister. But I would never do that with points since they cant change the dwell and I would think it would be harder on the condenser to control the points from arcing. I just wanted the original poster to know what I have been able to use. He has to use what he feels best with for primary resistance. I should go out and measure the primary current flow in my setup as I am very curious what it will be compared to what the stock system is. And I should check it with the key on and the eng running. Ron