Those rims will fit. I have 20x8.5 and had my doubts about them fitting but the website said they would. THey fit perfect with room to spare and no rubbing issues. Also, I had a set of nankang tires before on a mustang and had no issues with them. No they are not as good (road noise, water treads, tread ware, etc) as bigger name brands, but if you on a budget, they work fine.
Mods: 20x8.5 chrome/black rims, 245-35-20 Kumho ecsta 4x ku22, pioneer avh 4200 DD headunit, 1500 watt rms rockford fosgate (T1500-bdcp) amp, 2 rockford fosgate 12 inch (T1s), 800 watt rms rockford fosgate (T800-4ad), pioneer 5 way 6x9s ,pioneer 4 way 6.5s, 30% tint, black spyder headlights with 6000K HID (fog/low), K&N CAI, black altezza tail lights, and magnaflow exhaust.