The dealer is full of crap...as usual. There's hundreds of us that have been using the double platinum plugs for thousands of miles with out a problem. They just don't carry it at the dealers and want to sell you what they have. The old Champion number is #7440 for the Double Platinum plugs, the new number is #7570. They'll both work fine. Make sure you go for some decent upgraded wires too. The Crane wires from Race & Street are highly recommended.
http://www.raceandstreet.net/Merchan...ategory_Code=P
Oh yea, one more thing....please use the anti-seize lubricant on the plug threads and dielectric grease on the wire ends that go on the plugs...it will save you trouble in the long run.