Spark plug help!!

[jeffco]

I need help selecting a spark plug/heat range as a starting point for my race only 340. It has 13 to 1 comp with ported Edelbrock heads. Edelbrock suggests starting with RC14YC champions. What are your suggestions? The ignition is all MSD, 7-2 with matching coil and large cap billit distributor with 8.5 super conductor wires. I have heard more than once that resistor plugs could be damaged by the MSD'S much hotter spark, myth or not? Any way any help will be appreciated, jeffco