I have an '06 silverado with drum brakes in the rear and a 2/4 drop. I'm trying to figure out how small of a rim and how big of a tire I can use. I was hoping to use 15 inch rims and about a 9 inch wide tire. After entering my tire specs into HP tuners, I'm currently using tires with a heigth of 29.7 and I would like to stay as close to that as possible with the ET streets. Suggestions?