I am building a 454 with the 781 heads, after milling heads and putting in larger valves my CC is 115. I am trying to get my compression to 9 or 9.5 . with a .250 dome piston I am still at less than 8.5 I will be running a 69 corvette tri-power setup, and will be installed in my 68 chevy c10. what can I do to increase the compression.