I hope that I'm not too late to chime in... I am installing the ATS tall spindle kit with ATS C5 brakes. Because the money is drying up, I' installing the stock 17x9 wheels off of my 2000SS Camaro. They have been in the attic for the past 4 years. I have a 1.7 in spacer for the front, and a 2" for the rear. I think a 1.85 would be better for the rear, but the 1.7 is perfect for the front. I test fitted a 275zr40 tire in the front and the only place it hit when I jacked the suspension all the way up was on the sub-frame when I tuned it all the way to the left, on the drivers side. I hope that this helps I'll attach a link to the pic.
http://www.scarymaggot.com/itlbtu/PICT5634.JPG