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The resistor is to protect the coil when the arc at the plug occurs. An arc is basically a short circuit, so the more powerful the coil the more power the resistor has to be able to handle. Actually the power rating of the coil has more to do with the core material than the windings. The more core material, or rather better quality core material, the more energy gets stored in the core and thus transfered to the secondary when the contact breaker opens.
With CD (capacitive discharge) electronic ignition, the coil is actually used differently than with contact breaker or transistor assisted ignition. With CD, the coil is a step-up transformer rather than a storage of energy, and the different types of coils does not really make that much difference. I can't tell you where to get a CD ignition, but I do know how to make one (sorry, no facilities at the moment to make it). They are large compared to transistor assisted ignitions, and generate somewhere between 300V and 600V that gets dumped into the coil. This high voltage is why they are not so popular (difficuilt/dangerous to build/maintain), but they actually work better than transistor assisted ignitions, and typically are designed with multiple sparks (say 5 per ignition event, 3 at high revs). Multiple sparks can usually not be done with transistor assisted ignitions, because the coil is too slow to build up a field. Capacitors on the other hand can be charged up very fast, and that is why CD is so good. In fact, they dump the energy very fast as well.
As far as I know Pertronix is transistor assisted ignition with some fancy compensation for dwell time. As far as I know it does not start build up the field until a predetermined time before the next ignition event, as opposed to other systems (and contact breaker) where the field is started to build up just after the last ignition event. But don't quote me on this, as I am not 100% sure. But in any case, I would fit a Pertronix coil with a Pertronix system. That will be the optimal combination, as they are designed for each other. Coils are not the same, and even the potting material (e.g. epoxy) affect the performance.
So, no streight answer (as always), but shared information (as always). Have fun...
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