15s dont fit over a D60I think you should easily clear them unless you get crazy with the backspacing. 315x75r15's easily clear with just a leveling kit.
315x75r16 = 34.6x12.4" mathematically (1"=25.4mm) which is basically a 35x12.5
275x65r20 = 34.0x10.8" by math = easily clears.
Good luck! and WELCOME!
PS I am not sure about 2wd clearance, though.