What do you mean by "worn"? You put them in at .035" and 6000 miles later they're at .070" or what is it that you mean?
I'm not reading that you actually have a problem. "No fouling and plugs have a light tan on the ceramic!"
What kind of plug and heat range are you using?
I'm using AC R44TS and have had a stock GM HEI in the 292 for about 15 years. I usually change the plugs every five years whether I need to or not.
