Your stock coil will probably work fine. Pertronix instructions tells you how many ohms the coil needs to be. I can't recall the figure. If the ohms are correct, and your coil is healthy, no reason to replace it. Keep in mind the Flamethrower coil is available as a black cylinder, just like your factory coil is. It's a little glossier, but otherwise they really don't look much different. And you can peel the sticker off if you don't want it to say "Flamethrower".

I also believe, only from your brief description, that you might have a carburation issue, and not necessarily an ignition issue. That said, I am a fan of Pertronix and I recommend it.