@airdisc , absent any other data/details, if Govt. of India IT is using 2001 as the basis, then that is the best figure you have. And use that for the US filing purposes. Just keep records of how you got that figure.
Note that if the prop. was used for in come generation during your wife's ownership, then you would need to recognize any allowable depreciation ( for purposes of gain calculation and recapture).
Is there more I can do for you ?
Namaste ji
pk
