OK, let's go back to zero and figure this out. To figure static compression ratio, you need 5 figures.
727cc's in the cylinder @ 0.030"-over.
76cc's in the chamber.
9cc's in the deck, figuring the original 0.025" piston deck height and the additional 0.020" from rebuilder pistons. If you used premium pistons with the original compression height same as OEM, the compression height will be 1.560", otherwise cheap rebuilder pistons will be 1.540", resulting in 0.045" piston deck height.
6cc's in the flat top piston eyebrows.
8cc's in the gasket.
Adding these up totals 826cc's drawn in on the intake stroke. As the piston comes to TDC, this volume reduces to 90cc's. Divide 826 by 90 and find 9.2:1 static compression ratio.

The cam to make the motor work properly with this SCR would be in the 260-270 range, not 305. With the 305 cam, the intake valve closes too late to trap the already low volume of mixture and you'll be lucky to make 100 psi cylinder pressure. A 260-270 cam would make 140-160 psi with the 9.2 SCR that you now have.

If you want to use that 305 cam, or one like it, you'll have to rebuild what you have to make a 10.5-12.0 motor out of it to make the cam work right. Also, the 305 cam, even with the proper SCR, will make power from 3500 to 7000. Are you geared for this? Is this a solid lifter cam? 'Cause a juice cam will sign off at about 6200 when the lifters pump up.

Do yourself a huge favor and read this tutorial from Iskenderian....
http://www.iskycams.com/camshaft.php