what imfo do you need to tell compression ratio??

Bore (B), stroke (S), piston dish volume (can be +/-) (PV), compressed gasket volume (GV), cylinder head chamber volume (CV).

Compression Ratio = [(S*pi*(B/2)^2)+(PV+GV+CV)]/(PV+GV+CV)

If you want to get real exact, you can also factor in piston deck height volume(can be +/-), and volume above the top piston ring (between the piston and the cylinder wall).

A stock 87-93 5.0 is around 9:1 compression ratio.

x2 on this. There are some calculators around also. Usually drives me up a wall doing the chamber cc to cubic inches conversion.