18x8.5 front wheels..what backspacing?

[6D9]

I know with 18x8's that 4.75 to 5" is what most use. But with 8.5 in the front what do ya think?? I am guessing 5" to 5.25" would work. Anyone using this size?? My car has a 2" drop in the front with inner fenderwells. Front tires will be 245/40/18 BFG KD's. Thanks!