Please tell me these centercaps will fit my wheels

Send them an email and ask what size caps it uses. I'm guessing they don't take the standard large size caps, just like the FR500's don't. The standard large cap is what you've purchased. Those fit Mach 1's, Bullitts, etc...

The "minor modification" is taking the clear half of the cap that includes the pony off the mount and taping that to the other mount (after removing the clear part with logo on the other cap). The problem is that the emblem portion on the large cap is twice as thick as the emblem portion of the cap that fits the wheels, so it will stick out quite a bit. If that doesn't make sense, I have a picture I could show you.

I'm thinking the 2005+ stock caps might actually work. I just haven't wanted to cough up the dough to try them. I know that they're a lot more shallow than the large caps, and depth is the issue. I just don't know if they're the right width.

The other option would be a sticker. Maybe black with chrome GT logo.