You can tell they are the OEM R spec Cup 2's by the weight rating. Only way to distinguish from what I can tell. OEM front/rear will have a weight rating of 98Y/100Y, whereas the normal spec tires will have a 102Y/105Y weight rating.
When you search by model on the Tire Rack site, they automatically give you the correct tire. Michelin used to publish the actual tire part numbers on Michelinman.com, but they've stopped now. The 350R tires have less tread depth and they weigh less than the Porsche N-spec tires in the same sizes.
I wonder if they changed the compound on that tire? The RA1 and the RR have always been great tires. But when the 888 came out, they made us run them and they were quite possibly the worst tire ever. There was a massive revolt and then we went back to RA1's. They hopefully probably fixed the issue.
Yeah, I was not a big fan of the R888. Worked good for the first half of tire life and then fell off a cliff. Even when heat cycled properly. NT01 was a little better. I am willing to give the R888R a try as the reviews have generally been better then the R888.
Heck the label probably says it all with the "R" suffix. The old ones were good for about 1 heat cycle as I recall. Somewhat related, their badass truck tire supposedly shared the same R compound as the RR slick. I thought that was cool.
I will be mounting them to the stock GT350 wheels (10.5"f, 11"r). 295f and 305r are the ideal sizes. They are smack in the middle for those rim widths so they should fit and ride perfect.