What gap do you run them at? i am running a Pertronix ignitor. Also would the resister version help on the Pertronix ignition?
I'm running OEM Lucas cap, Ignitor, stock coil, stranded copper core wires, resistor plug terminals and Champion RN12YC plugs (both the terminals and plugs are 15KOhms, I believe). Book gap is 0.025," I run at 0.028". I don't think the Ignitor cares about the secondary resistance--that's mostly to mitigate EMI and the wires are electrically isolated by the coil--but there is a spec for coil resistance (IIRC it's 1.5ohms). I've run this setup for at least 100K miles with no issues; the only ignition problem I've had was an aftermarket distributor cap--I think it was Bosch--which arced under load and caused an intermittent miss.
Side note: I have an Aussie 'internet friend' who wanted to surprise one of his mates doing a concours resto with some OEM Champion plugs. The only ones he could find were a couple sellers on eBay, but they wouldn't ship to Australia. So, he had them sent to me and I forwarded them to him. Might have been that last .01 point at concours