Chances with harvard/stanford with a 3.9 unweighted?

Well some people don't get into Harvard with 4.0's, did you take any language cl? If not that's going to cost you. To get into an Ivy League school you should have taken at least 4 years of a language. Do you have a job? It will be taken into account when being considered. You should also increase your SAT scores, many potential student with perfect 2400 are rejected. Same with you ACT. Start on your essay now. After all that you are unlikely to get in, but do your best. Present yourself in a way that it will be their loss if you are not accepted, without sounding like a snob or arrogant. There is always room for improvement so work harder.