No need to test fit. The 8.8 is 3" wider than the 7.5 thats under it now. There is less than 1.5" per side clearance between the side wall and fender lip so I know it wont fit if I lower the truck any. It would fit at stock ride heigth but the tires would stick out flush with bed sides and would hit if the rear ever compressed enough.
I'm running a expo disked 8.8 with 17inch svt cobras, all i did was roll the rear fenders a bit with a bat (rolled smooth and clean) and it cleared perfectly. well until the axle bottomed out on the bump stops haha never had a rubbing issue.