It most likely will, but Swiftech seems to have inconsistent compatibility info. Their compatibility list shows it is designed for GF 8800s and lower, while the 'recommended accessories' lists a GF 9800 mosfet heatsink.
I think it is compatible with the factory card. If your's isn't, then you may find that nothing works.
I'll try to help with that. I have an MCW60-R, and it fits on the reference 9800 GTX.
Okay, now for the more difficult stuff. We have our four mounting holes:
Diagonally these are 75 mm apart center to center. That's about 1/64 of an inch under 3". Horizontally and vertically they are 53 mm center to center or 2 1/8".
If your holes match, then this block will work for you. When measuring, don't try to find the center of the screw/bolt/hole/whatever, measure from the side to the side of the bolt. Example: for the diagonal, measure from the top-left of the top-left bolt to the top left of the bottom right bolt.