Camshafts, idle quality, driveability and LSA-REAL WORLD EXP and OPINION

Time for my dumb question. I have been following along in this thread and I have a question for you cam guys. Assuming and engine is 340 CI and is running "Cam-X" and it works great. Now let's make that same engine 400 CI. IF we got to the new CI by a longer stroke, wouldn't you need a longer duration cam to take advantage of the longer stroke? Now the second part of my question: let's say that we got to 400 CI by boring the cylinders and keeping the stroke the same. It would seem to me that the original "Cam-X" would be ok since the piston/valve timing would essentially be the same as stock. BUT, you would still need some way to fill the larger hole. Could you not keep the duration basically the same as "Cam-X", but increase the lift to accomplish filling the cylinder? I know that is pretty basic info and there are many variables, but I was trying to get the idea concerning the different ways to get larger Cubes and how the difference between increasing bore-vs-increasing stroke affects cam selection.