Really need to think about these questions and ask yourself what your usage and purpose intended for this build. Using sleeves may be your best bet if you are only thinking about building the 340, as opposed to the 360 roller build suggestions?
Also are you aware that the max overbore limit for a 340 block - according to the factory service manual specs - is .040 overbore? Going further with overboring increases your chances of overheating, among other things?