[ERA Chas]

Wayne,
No insult taken in spite of my strong post. I am simply frustrated and thought ordering from Summit is painless, a two-day affair and I was hoping a trial of these plugs was indicated. If not good for you-you're no worse off than now.

The really good part of the process for me was the give and take with Brandon Peeler, the NGK web tech. He really delved into my combination and came up with the FR4's.
He hit it perfectly-first time- which I guess I could have conveyed better to you. I didn't contact Shelby, my head mfgr-I thought the plug-side of the equation might work better so I searched Champ, Autolite, Bosch, Accel-all the bigs. I couldn't get apples/apples heat range comaprisons-even after looking at 1000 cross ref charts and apps like 'Ford, 1965, Galaxy' then get the 13/16 old style plugs.

If you tried them, I was hoping you'd be as successful as I was and spare you a lot of monkeying. You can still try them when time permits.

ALL of us here will have different heat-range requirements and one-plug-fits-all will not get top performance.

Good luck.