Pertronix does still make some coils that take a resistor, but hopefully yours is one of the full-voltage kind. Check the label to see what it says. Or get the part number and ask Pertronix to make sure.
But I'm with spatacuulous, you probably don't need one and the Painless most likely is running the full voltage. And you wouldn't need one just to get the thing running and test for spark anyway. The reduced voltage of a resistor is just to help the older coils last longer. Even an old original coil would still spark with 12 volts.
A coil that doesn't use one has an internal resistance that's compatible with 12 volts and will sometimes list that value on the label.
What's the actuall problem you're having? No spark at all? Erratic spark? You didn't mention what exact ignition system you're running. Electronic or points? Factory or aftermarket? Or is there a Flamethrower ignition system and not just a Flamethrower coil?
Paul