Definitely try a practice ACT. Both tests are about 3 hours (2 hrs 55 for the ACT), but the ACT has 215 questions while the SAT has 154. The ACT questions are generally more straightforward, but you have less time. Also the “Science” section in the ACT really is about reading graphs and charts.
What were your component scores on your SAT? Was at least 1 score in the 700’s? Do you know where your mistakes were? Were they silly or careless mistakes on easier questions, time issues or were you just unable to solve the problem? For MIT and Stanford, the 25th percentile for Reading is 720/700 and for Math 780/720. These are the scores you need to shoot for.
The only way to improve your scores that much is to eliminate almost all careless errors and have the substance pretty much nailed down. It is a function of short drills on particular sections where you may be weak and then at least 2 full practice tests in “testing conditions” to get speed, familiarity and knowing how to avoid careless mistakes down. It’s doable, but in the meantime, you might want to lower your sights a bit as far as “match” schools are concerned. If you are content with ASU, you do have some leeway to shoot for reach schools.