Piston area × PSI in the cyl = pounds force on the piston, which is almost directly transferred to the con rod.
Now in that, any one cyl block can only be poked so far. Also, is this question limited to boring, or comparing the torque developed between two engines of equal displacement? Are the cylinders in question being supplied through the same size ports and valves, or larger valves that the larger piston allows before cyl wall shrouding?