I can try to help you, but I am not sure about the Layout of your card:
In general, the 55nm Waterblock is incompatible with the "old" 65nm, because they have a different layout.
I don't know if there has been a change of the layout by Zotac, but normally all standard cards are compatible. Exceptions are maybe some overclocked cards (not EVGA, XFX) or with bigger RAM. But I do not know this for sure, because I never heard/had/saw of one.
I would guess, that the AquagrafX 55nm is compatible, but you should make sure
by looking for the bare plate and check the places of the transistors and RAM. (These are in reference layout, search your one and compare)...