[Bruce Edwards]

When I use the Edelbrock heads I use what they show in the instruction sheet and change it from that point when needed.
I install Champions in Edelbrock head engines. Never had a failure and that is a big thing with me. I stay away from all the "fancy" plugs and use Champions, Autolite, and AC depending on the engine. Not a big fan of Bosh, NGK, split fires and the like. Also if you are not running fuel injection stay away from platimum tip plugs. You need more surface area with a carb engine to keep the plug clean. The small tip plugs tend to fowl out easy the extra fuel carb engines use at start up.
Install the RC12YC's and see how it does. That is what is in Dave's 351W with 425HP andhe has been driving it for over 2 years now and the plugs still look like the day I put them in. That is also what is in Bill's ERA 289 FIA.
Like I have said I tend to stick with what works.