I have exactly the same need. If you check
www.XFree86.org it is clear that the 7000 is not supported in XFree86 4.2.x supplied with Red Hat 8. It is supported in XFree86 4.3.x that comes with Red Hat 9. And I confirmed this with a perfect install of RH9 with the 7000 correctly recognised (not as a VE). I have sent email to XFree86 to determine if you can install 4.3.x on RH8. I will let you know the answer.
Remaking the kernel as per the previous post seems a big deal but please let me know if you tried it and it worked.