The longer stroke cranks with 400 mains seem to do fine if it is a good steel crank.

I know Rich Eherenberg did the "over bore" mains on a low deck MA project car and don't know of any problems... perhaps he'll post.

If you have already bored the mains oversize, I'd put it together and run it. Otherwise, it might be easier, cheaper, better(?) to simply get the crank turned down to low deck size mains.