The only two values that you can't get from a catalog or spec sheet is the true size of the chambers and where the top of the piston will sit in relation to the deck.
The chamber volume is easy. Get a 5" square of plexy glass and put a small hole in it off center. Grease it up and stick it over a chamber on your heads. Using a graduated in cc's syringe you can pick up at the local pharmacy measure how many cc's it takes to fill the chamber with water (or your favorite liquid).
The machine shop that has you block should be able to tell you your deck height (if they can't I would get your block to another machine shop fast).
Subtract 1/2 the stroke, the center to center rod length and piston compression height from the deck measurement and you wil have the distance below (or above the deck the pistons will sit). Actually a good machine shop will do these calculations for you.
Plug the numbers into the calculator and you will have your compression ratio.