There are several places that sell heat shields for spark plugs. Here is just one of them. They are used on race cars so they should work all right on ours.
There are others, but I can't find the site right now. I also have no financial interest in this product, except I might try them myself.
Spark plug heat shields
or if you dont see a hyperlink just check out this address:
http://www.thermotec.com/tt/shield.html
When you get there, just click on the red arrow at the bottom to go to the next. I think there are three different types.
Marc L.
60 4drht