What are my chances for Harvard or Yale or Stanford law school with a 4.0 UGPA at LSU and a 170 LSAT?

On numbers alone, Yale is probably a little bit of stretch. That particular institution truly does have their pick of the litter when it comes to applicants, and this is reflected in their high LSAT median of which I believe is around 175.

Harvard on the other hand, you will have better chance at, but there admission statistics are only slightly lower than that of Yale.

Stanford is a little bit of a wildcard. While your numbers of well within their range, Stanford tends to place a much stronger emphasis on what you can contribute on a personal level. That being said, having an exceptional personal statement and resume will go a long way.

That's my two cents.