Think its some were around 7.8/9:1

but this depends on head thickness being around the 139 std (unskimmed)and the type of gasket used as a cometic is 1.3mm thick and that also lowers comp

the only true way is to measure cc's (compression)
only way comp will be std on 2wd pistons is if the head HAS NOT BEEN SKIMMED!!!!!

Also if i'm right 2wd pistons have the central piston pin design so you will notice piston slap when cold

hope this helps