I got my oculus rift when I had a GTX 980 and was very happy with how well it worked, have since bought a second hand ex mining 1070 for cheap and can't really say there's a noticeable improvement. So yes the 980ti will work well.
The CPU might be a little bit marginal, I'm not sure. You can run a compatibilty test available from oculus (Vive might have one as well?) and Steam has a VR test you can download. I'd recommend trying those before buying a VR headset.