Larger bore than stroke length is called over square and is usually high revving. Bore and stroke the same is called a square engine. Smaller bore than the stroke is called under square an is usually considered to be a higher torque engine.
I agree with every thing Jennifer said. I worked my whole career as an automotive machinist and that was how we did it. A very tiny valve ,if there is enough margin, you can cut a groove across the head of the valve and use a screw driver as a lapping tool.