Depending on the track and the speed, 70hp might do it, or might not.
You can have your block bored to accept 4.25" pistons. Makes 298ci with stock stroke. Along with carb work, cam work, and head work, that should get you 65-70hp.
If you are limited to pump gas (93 octane) then you had better stop at about 9:1 for compression. If you are allowed better fuel, 11 or 12 compression works a lot better.
If you want to turn 2500rpm you will need considerable carb work and a custom cam to match that engine speed. Many people will tell you that your motor will live a lot longer if you stay at 2000rpm.
If you are allowed, a 450 head will help too.