On todays pump gas with iron heads I wouldn't run more than 9.75 to 1 compression ratio
Building a 4 inch stroker motor will reach your goals easily
With your present (stock stroke)combination I would use a Eddy RPM air gap intake and a good 750 CFM Thermoquad and a cam based on the peak torque RPM goals BTW, the last two NHRA legal 340 stocker motors I built and dyno tuned made 420 HP with the J heads and 430 HP with X heads My freind who held the NHRA E and C stock records made a little more power(450 HP) on the same dyno as mine did He did a lot more parts testing to get those results though