Will these fit on the AWD model or will there be clearance issues because of the wider rears?

anyone know?

 

Don't use staggered setup on an AWD car...will hose the drivetrain. 18's of the same size should be fine though.

 

actually, staggered is no problem, as long as you maintain the same overall diameter. the setup from is350 won't work though coz' the rear wheel diameter is larger than front. that will mess up the awd system. but if you have a set of staggered setup front and back, and get tires accordingly so overall diameter is the same, you should be fine

people did it on the gs300awd already

 

Rominl is right. You can have the stock wheel of the IS350, all you need to change is the front tire size to 225/45/18, the diameter will then be 26 inches front tires. They will match the diameter of the rear tire perfectly.
Here's the tires calculation link: http://www.miata.net/garage/tirecalcold.html