An inch is about right. Measure your backspacing (lay a straight edge on the backside of wheel and measure from it to the hub mounting surface) on the new wheels and compare that with your factory wheels. Whatever the difference is will be the size spacer you will need.
I'm currently running wheels on my '95 that were designed with '05+ backspacing (18x8.5" front and 18x10" rear). I run a 6mm spacer (.25") up front to clear the Cobra brakes and a 25mm (1") spacer out back.