As SRStaff said SLs with IFS do not give you room for larger tires. This is because when you compress you compress straight up and still compress as much as you would at STOCK height. So yes, they will fit at ride height, but as soon as you hit a bump or compress for another reason you'll rub.
This is why BLs are popular with X's as they increase the space your tire has to compress. A 2" BL will allow's a 33" tire to be fit comfortably.
You should be able to fit 32s though, not just a 31.5" with your Rancho Lift.
So to answer your question:
You'll either need to cut your front fenders (quite a bit) or get a 2" BL in order for the 33s to be able to compress properly.