I'm running 17x8 Mustang Cobra rims and I have to run at least 1/2" spacers on the fronts to allow the "hub caps" to fit over the spindle.
I'm actually running slightly thicker, as it:
a. Puts the track in the OEM location
b. Allows full lock to lock steering - with rims bolted directly to hubs, my tires will make contact.
Rear would be a bolt on; but again I am running spacers there so inset is same front and back (although, I have since learned that the Gen 1 4x4 w/Dana 35had 3" difference front to back and never really noticed...)