Larry,
Not very many miles, under 1000 as my car is more garage art. However they have been in the car for over 2 years with no problemo whatsoever. I had even removed them late last year to see if they fouled (as I needed a carb idle screws adjust at the time) and they were perfect.
Still perfect.
I have a 750 Holley Street Avenger. My friend Steve who restored my car was a senior engineer GM Corp (retired) > working at the Mesa fuels test facility. He knows more about carbs, plugs, fuels, etc. than the average bear. If and when I would replace those plugs I would go exactly with the same.
Dave
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