For anyone interested, I found the original type Dill 630 gray stem caps used on my 04 Mustang (and other year Mustangs/Fords around that time). Specifically, they were used on the 04 Mustangs with the Anniversary Package option, to match the silver radio antenna, silver frost license plat screws, chrome key lock on the driver's door, the silver door lock knobs, etc. They were also used on the Mach 1 models. It took me several weeks of research and searching. Here is a pic. They look more blue in the pic, but they are the silvery/gray color.