Since a 34 is in the top 1% already, I don't think there is a good reason for you to take the SAT. Instead, work on improving your scores on the three ACT sections other than English. Incidentally, some colleges accept the ACT plus Writing as the equivalent of the SAT plus two subject tests.
If you decided to try the SAT, you should try any of the tests 5 through 8 since they are tests that were administered. They are free to print from the College Board. You should also do about the same prep you did for the ACT and take the practice test in a setting comparable to the ACT setting, perhaps a quiet library.