Which spark plugs to use?

[fred cook]

In the near future, I am going to do a rebuild of my 3.0 SC engine. The new configuration will be 3.3 SS using Mahle 10:1 pistons, LN cylinders, Carrera twin plug heads w/XDi ignition and 964 cams. The question is, what heat range spark plugs should I use? The engine will be limited to 7,000 rpm so very high engine speeds will not be an issue. The heads are set up to use 12mm plugs.

Thanks,