The coil and the resistance that you require depends on what ignition system you finally end up with.
The original duraspark II distributor with a original duraspark II module requires a approximately 1.05 to 1.15 ohm resistance in the coil circuit with a original DSII type coil.
I used a original DSII distributor, but used a GM HEI module instead of the DSII module. I also used the original TFI coil. This system requires no resistor, just like the Ford TFI does not require a resistor.
When you call pertronix, see what they say about the resistor. I think some of their modules need the resistor, some don't. If you have the instructions for your unit, see if it talks about having or not requiring a resistor.
I am not sure about the other distributors and their modules and whether they need a resistor on not. It all depends on the design of the module. Some have current limiting built into the module, some don't and require a external resistor.