JOEL - I agree that it is the "opinion" of many LDS that the Mayans, Olmecs, Toltecs, etc. were the Book of Mormon people; and perhaps they're right. However, opinion and fact are often two very different things.
Even though I am a scientist by profession I am able to accept all church doctrine, scriptures, and gospel on faith as witnessed to me through the Holy Ghost, but when it comes to scientific/archaeological things I need validated evidence and facts to support such claims. So far no reliable physical evidence has been found that directly links those civilizations to the Book of Mormon people, only circumstantial evidence.
In my opinion the only "clear evidence" for the truth of the Book of Mormon is the positive effect it has on our lives as we live by its teachings and through the witness that comes to us from the Holy Ghost.