Which Plug for C302B Heads

i use the ngk r5671A plugs, say 6 or 7 heat range ?

There are alot of choices for plugs. I myself have always had good luck with Autolites, my personal choice is to run a resistor plug, one or two heat ranges colder than stock on high performance engines. Also I would open the gap up to around .045"-.050" when using a CD (MSD) ignition.
Jeff

As important as the gap or the brand is the fact that SVO heads require a 5/8-reach plug. Running a 1/2"-reach plug as in the iron heads will leave 2 or 3 threads at the bottom to collect carbon and act as hot-spots for pre-inition. I use easy-to-locate resistor-plugs designed for the aluminum-headed Corvettes, which also uses a 12mm plug with a conical seat like Ford/SVO. Currently, I have Champion RC12 YCs, but I've also used Autolite and AC. All work fine.

Thanks for the replies you guys, I pulled a plug and it was an Autolite 3924, I'll check the gap tonight.