So here is where I think I got confused, which made me originally post this question. Upon further investigation, the 18"x9" SVE drift with a 275/40/18 has a sidewall of just 4.33 inches, with a total diameter of 26.66 inches. A factory 18" rim with the 235/50/18 setup has a sidewall of 4.626 and a total diameter of 27.25. So in other words, the reason why it looks like a 19 is that it's because the setup is overall a smaller total diameter. In fact, its noticably smaller than the 19" setup on the Performance Package.

While it looks great, I wish it wasn't loosing some much over all tire diameter.

 

When these came out out I actually called LMR and asked about those 18's. they said the car belongs to an employee there and he has an eibach prokit on there as well which i beleive gives pretty aggressive lowering. more pics here:
http://www.flickr.com/photos/latemod...n/photostream/

 

Actually, to hell with those wheels. I'm getting THESE wheels:
http://www.americanmuscle.com/charco...18x9-0512.html
http://www.americanmuscle.com/charco...8x10-0512.html

Better fitment. Similar price. A bit better looking, IMO.

I keep changing my mind!!!!!

 

They are 18's, look at the photo and the tag on the tire. Norm made a good point though on how to figure out if it was an 18 or 19 wheel, but I think we didn't account for the suspension drop.

 

I'm interested in these, but I have a v6 convertible and not sure that 275's would fit it. I've heard other Mustang enthusiasts say something about brake stops for the front wheels, and that the v6's weren't set up for really wide tires like the GT's.

I thought about getting those look alikes on the American Muscle site that are 18x8. I already have other 18x8's with 245/45 tires on them.