What do you mean *a stock top end*? Over boring isn't going to net any power gains. If you want more power have it ported when you take it apart with complementing modifications. Carbs, pipes, intake and filters etc.
I'd go with wiseco pistons, but as far as a stock topend, I'm not sure what your getting at. After market piston, bored only if needed and good seals, gaskets, bearings etc.
Go through it good and make sure everything is cleaned and assembled right and you'll have a good running motor.
SP