Is your block the early 71 230 casting that has the big main webbing? If it's not it's still a good block and 700 HP isn't hard on them if it's a super solid block and at that hp level you'd want to keep an eye on the main caps. Other than that we built a 451 at work a few months ago with the 440 source kit it has a 1.320 ch piston I think they have them listed at .025 under deck. We had to deck the block .028 passenger side and .032 driver side.
I wouldn't bore your mains out to 440 size.
Anyways it might end up being hundreds of dollars cheaper to just buy a kit from 440 source. I know that from experience lol. But I wanted a little higher quality rotating assembly (after seeing 440 source stuff 1st hand I'd buy it)