You could always just apply for a vanity plate, and use your GMRS call. Most states adhere to the 7 character format so, as long as you're within those parameters, you *should* be able to get what you want.
I do have to agree with WRUE951, however, that you want to be careful who you cut off in traffic. Our licenses, both GMRS and Ham, are public information, and there are a LOT of nutjobs out there. I've opted to keep my calls off my vehicles for this very reason. But that's just my 0.02.