If your points are set up well youll notice about nothing when fitting the Pertronix, BUT it does make maintance easier and cheaper once its fitted.

As far as coil, doesnt make much difference, most of what people claim is in their imagination, We tested 7 different coils way back on a mildly tuned 350cid and they were all within 1-2 hp of each other... now changing to a MSD CD or similar does make a noticable difference, especialy mid range and fuel consumption.

One thing to be very careful with is fitting a hard core low ohm coil (ie the blaster SS) to the pertronix, you land up having to run a massive ballast resistor (1.6ohm), if you dont youll pop the pertronix.

I would say for regular mild motor just run the pertronix on the stock coil unless it fails.