well the most that you can bore the bata II is it 83mm that would be a .040 over. Most of the turbo guys to bore over, but only to 82.5mm a .020 over. That is because there arent many low compression pistons out there to fit the stock bore.
i got my block sonic tested and the thinest spot is .109 aand the most the guy will over bore is .020 over and he doesnt want to go that far. the wall thickness is so inconsistent its rediculous. thickest spot is .265 there is .100 difference between top and bottom on a side
the pistons were gonna be coustom made so that wasnt a big deal