Juat sayin Hi Thumper. To Cab; I'm not sayin don't run extended core plugs. Just sayin they will run hotter, all else being equal. Ran them in my wedge motors all the time back in the day. They helped to solve a lot of problems such as poor intake runner and combustion chamber design, poor fuel distribution, weak ignitions, etc. A lot of them lived due to high octane leaded fuel. If you can run them and don't end up with the attached pic, by all means, run them. BTY, the pic is the result of running a way wrong heat range plug - and running a little lean.