This is exactly what I was afraid of. I had my wheels made by American Racing and they will do any backspace and bolt pattern so I bought a Wheel Fit Tool and used the Marugen flares and found 5" BS was perfect, which is -6 offset (on a 17 x 9.5 wheel). WAY different. The fronts are 17 x 9 and 0 offset. They could use about another 1/4" of poke though. Tires are Conti DWS, 245 and 275.
I'll post a pic with everything mounted and on the ground next week, the flares were just painted and have yet to re installed. The attached pics don't do the fit justice.