normal standard for sea level atmospheric pressure is 14.7 psi------

so using a rule of thumb----7 psi would aprox add 50% to your compression ratio and 14.7 would double it---------however, since normally the cylibder doesn't start compressing the charge until the intake valve closes your dynamic compression ratio is less than the static numbrs but if boost is added, you are getting pressure into the cylinder more effiently and those figures get disturbingly distorted-------

I have had several tow vehicles power by 460 and you don't need boost or 4.5 strokers-------advance cam for early 1970 numbers (pre smog ), good dual exhaust system, Holley 850 carb with dist advance changed to 10* meckanical so you can run a quicker curve with around 36 * and tow away-------My old 1970 F250 which I put a Lincoln 460 into has been in many drag racing publications and the Jim Dunn funny car movie--