How To Figure Compression Ratio

With that much stroke, you need the dished pistons for pump gas. A flattop might be as much as 12 to 1.
You could check a compression ratio calculator (I like the one at Wallace racing calculators) and see if you have enough info. I realize MOST of the info you'd have to use would be guess-work. Probably most important spec would be the dish volume, kit info might have that for you.
Comment above is correct. To get an ACCURATE comp ratio, everything has to be actually measured.
(You can possibly get an idea how much the heads have been shaved, maybe. The outer row of head bolt holes are 1" thick stock. If you can measure them now, and get, say, .950, head has probably been shaved about .050.)
And there is NO direct correlation between cranking pressure and compression ratio. WAY too many variables.