Torque is more useful for cruising and tire fryin' than HP. If you push up near to 10:1, you will have plenty of torque. It won't be awful at 9; you just want to not be below 8 if you can help it. But, ultimately you need look at your DCR because the other end of too much CR is to get into detonation. That is the point of discussing the cam; a smaller cam will increase DCR.
Correction on the milling amount: You drop the open chambers 1 cc for each approximate .005" of milling. So dropping 8-10 cc's is easy by milling .040 or .050".
If you drop to 64 cc, then your SCR is around 9.8 and your DCR with that cam is 7.9 with the ICL at 106. You might squeeze more on the DCR but you have to be careful on tuning and will have especially keep the timing curve limited. I assume you can get 93 octane there, as you will need to use it.
AL heads have an advantage in avoiding detonation. And closed chambers like the Edelbrocks or Indy heads have better detonation resistance. So those are options. Both breathe much better than the stock head.
