I would just go on tirerack.com and look at the specs to get the narrowest LRR size for your wheel width, they all have a range. Some people are of the opinion that taller is better for gearing as well as road hazards and slowing down the odometer, I'm of the opinion that shorter is better for less weight and lowering makes better aerodynamics without costly suspension upgrades. Assuming you have 5.5" wide rims I would go with
http://www.tirerack.com/tires/tires....=yes&tab=Specs