I see confusion here. The wheels in question are the truck Ralley, not the Corvette Ralley/Disk Brake Wheel. The caps do not interchange. There's 2 oprions, 1, get the oe style like what Wrenchbender says, or, if you don't mind doing some hunting for the special lug nuts, you can use the late model style caps. I have done that with the Ralleys on mine, using the '94-'98 4x4 style caps with the Bowtie in the center. It does reguire special lug nuts with the outside threads for the retainer nut/caps that hold them on. I think Napa might be able to get them, I found mine at a car show.
Center Cap 
