I've seen some people post over here before about having problems finding lugnut covers that fit when running stock rims and ARP studs. I've been able to find some at Napa that are 15mm longer than the stock plastic lugnut covers and should work with the longest studs you can find. The Napa part number is 641-1536, and are 99¢ each, and are available in grey (dull silver) as well. If you find you don't like how long they are, they have several other styles that aren't quite as long and should work, although the shape of the body is a little different.

Comparison of stock -vs- long lugnut cover
Another comparison shot
Picture of them installed on the rear GS rim
Picture of them installed on the front GS rim

They're long, and the pictures don't show it well, but they look OK. No need to tell me how dirty my wheels are, I already know!