I ran 1.25" spacers behind my moabs with 315's. On my other Jeep (2004 TJ parts Jeep) I have a set of 305/70-16 ProComp AT's that I found cheap on CL running on a set of clean moab wheels. They are too wide and actually hit the rear spring towers without spacers, I don't recommend that size tire. Regardless of 285, 295, 305, or 315, make sure the aspect ratio is 75 or 80.
Since we are talking Moab wheels I should mention there are several small variations, machined finish, painted finish, silver windows, grey windows, stepped windows. Seems they changed each year between 2003-2006, different for the Sahara edition. The set I currently have are the correct 2006 Sahara Rubicon wheels with machined faces and dark grey windows and they are nearly perfect! Make me an offer if anybody is interested, they would make a nice upgrade for a worthy Jeep. I just don't have a worthy Jeep...