Those Bestop flares only get you some tire coverage with additional width , no clearance . I've got a set , they were on my 88 for a couple of years w/ 4.5" RE springs and 33's , the tires rubbed when the jeep was flexed. The Bestop flares are on my 94 YJ now , it's spring over and runs on 33's , clears fine like that , I could easily fit larger tires but that would only invite axle breakage and other problems. Both Jeeps have extended bump stops. The 88 still has the RE 4.5" springs ( nice !) but now has Bushwacker cutouts. My plan is to install a 1" body lift and trim the fenders , this is in preparation for my newly puchased 35's, this will get me the lift , flex and clearance I'm after.
33's need some carefull planning to get proper clearance , especially if you start flexing it out.