Resistance is NOT evil.
The coils will function with plug cap resistances of 0 to 10000 ohms.
I recommend at least 5000 ohms for two beneficial reasons.
1) It broadens the spark duration time to help the ignition burn.
2) It lessens the radiated emissions for reduced interference with other electrical/electronic devices, making you a nicer cohabitant on this planet. Energy radiated is energy not used to ignite your burn cycle.
There is some interaction with the form by which the coils are triggered; points, points eliminator transistor, or active coil pulser. You don't say which you are using.
Cheers,