Appropriate Wheel Offset for 18" Wheels?

Holy crap! That's a lot wider if that's right. Yes, the stock rear end should have been 57 1/8". I didn't realize the rear disks moved things that much, you may want to ask Cass about that.

As far as 0 offset working, nope. If your measurements are right, you'd need a 24mm offset. to put the wheels back in the same place.

Yeah, I've measured it twice now... The rear end is completely assembled in the car including the brakes. I avoided the center section hump by measuring from the top of the pad contact surface to the top pad contact surface (~55.5") on each rotor. Then I measured from the pad contact surface to the wheel surface (~1.75") and multiplied by two. Adding it together gets ~59".

Maybe I should skip on these wheels. That being said, at least I'll avoid a 1.5+ hour drive home from the shop. :D

I think my best option, as of now, is to find a wheel with a good enough backspacing where I could run no spacer or a spacer on either the front or back. Maybe an 18 x 9" with 255/40/18 and 24 mm offset?