Do a search on "denso and iridium" to find more. A lot has been covered on these and also the NGK plugs. I think I may try a set of the iridium plugs this season, myself!
I run the denso IT20s in my bird. They run great. I was getting some bucking under high boost with platinum Motorcraft plugs and I never had it again after putting in the iridiums.
Do a google search on the web under denso iridium and you should be able to find a place to get them. I ordered mine online by doing that.