The Shrock front bumper will push the front down at least an inch or more. IMHO, I would not use spacers up front if you're getting a Shrock front bumper. Instead, I suggest getting heavier-duty coil springs up front.

For the rear, a longer shackle will work. Some people have opted for an Add-A-Leaf (AAL) kit and/or shackles in the rear. If you go too high, you may need a shim in the rear to correct the pinion angle.

As for the 285s, I have read that they will fit stock with a minor "melt mod" to the plastic on the inner fenderwell. For more on this topic see either the 2005+ forum here or go to www.thenewX.org