[bobcowan]

I always used a standard Autolite 3924 copper core plug. They're easy to find, inexpensive, and work well in all conditions.

You have to change them about every 25-30K miles. But for most Cobra's that's every 5-6 years or so.

You can spend a lot more money on iridium and platinum. All that does is extend service life. And some ignition systems don't do well with those types of plugs.