If your going to aluminum heads you can raise the mechanical compression ratio a little bit and still be safe on pump gas, I wouldn't though Keep it safe at 9.5 to 1 and use the O.D. ratio on the blower to make more power on better fuel when you need it
As far as what is safe at 8 lbs. of boost will be determine buy which spark plug heat range, how much timing, the jetting and the local weather conditions, if it starts to not feel right, lift up your right foot!